Andrei G Lebed
 Professor, Physics
 Member of the Graduate Faculty
Contact
 (520) 6261031
 PhysicsAtmospheric Sciences, Rm. 365
 Tucson, AZ 85721
 lebed@physics.arizona.edu
Awards
 Lenin Komsomol Prize in Physics
 Government of the USSR, Spring 1990
 Fellow of American Physical Society
 American Physical Society, USA, Fall 2014
 Landau Institute 1st Prize
 Landau Institute for Theoretical Physics, Moscow, Russia, Spring 2001
Interests
No activities entered.
Courses
202425 Courses

Accl Intr Optics+Thermod
PHYS 162H (Fall 2024) 
Intro Optics + Thermodyn
PHYS 142 (Fall 2024) 
Intro Optics + Thermodyn
PHYS 143 (Fall 2024)
202324 Courses

Hnr Intro Rel+Quant Phys
PHYS 263H (Spring 2024) 
Thermal Physics
PHYS 426 (Fall 2023)
202223 Courses

Hnr Intro Rel+Quant Phys
PHYS 263H (Spring 2023) 
Theoretical Mechanics
PHYS 321 (Fall 2022)
202122 Courses

Thermal Physics
PHYS 426 (Spring 2022) 
Condensed Matter Physics
PHYS 560A (Fall 2021)
202021 Courses

SolidState Physics
PHYS 460 (Spring 2021) 
Condensed Matter Physics
PHYS 560A (Fall 2020)
201920 Courses

Thermal Physics
PHYS 426 (Spring 2020) 
Statistical Mechanics
PHYS 528 (Fall 2019)
201819 Courses

Thermal Physics
PHYS 426 (Spring 2019) 
Statistical Mechanics
PHYS 528 (Fall 2018)
201718 Courses

Thermal Physics
PHYS 426 (Fall 2017)
201617 Courses

Hnr Intro Rel+Quant Phys
PHYS 263H (Spring 2017) 
Thermal Physics
PHYS 426 (Fall 2016)
201516 Courses

SolidState Physics
PHYS 460 (Spring 2016)
Scholarly Contributions
Books
 Lebed, A. G. (2008). The Physics of Organic Superconductors and Conductors. Springer (Berlin, Heidelberg, New York).
Journals/Publications
 Lebed, A. G. (2020). Breakdown of the Einstein’s Equivalence Principle for a quantum body. Modern Physics Letters A, 35(20), 2030010.
 Lebed, A. G. (2020). Fourfold anisotropy of the parallel upper critical magnetic field in a pure layered dwave superconductor at T = 0. JETP Letters, 111(4), 239.
 Lebed, A. G. (2020). Restoration of superconductivity in high magnetic fields in UTe2. Modern Physics Letters B, 34(32), 2030007.
 Lebed, A. G. (2019). Breakdown of the equivalence between gravitational mass and energy due to quantum effects. International Journal of Modern Physics D, 28(12), 19300201  193002022.
 Lebed, A. G. (2019). Layered superconductor in a magnetic field: breakdown of the effective masses model. JETP Letters, 110(3), 173177.
 Lebed, A. G. (2019). Unconventional fieldinduced spin density wave phases in quasionedimensional conductors in high magnetic fields. Physical Review B (Rapid Communication), 99, 041103(R)1  041103(R)5.
 Lebed, A. G. (2018). Destruction of the spindensitywave phase by magnetic field in a quasionedimensional conductor. Physical Review B (Rapid Communications), 97, 220503(R).
 Lebed, A. G. (2017). Inequivalence between gravitational mass and energy due to quantum effects at microscopic and macroscopic levels. International Journal of Modern Physics D, 26, 1730022.
 Lebed, A. G. (2017). Quantum limit in a quasionedimensional conductor in a high tilted magnetic field. JETP Letters, 106, 509513.
 Lebed, A. G. (2017). Response to: Comment on “Does the Equivalence between Gravitational Mass and Energy Survive for a Composite Quantum Body?”. Advances in High Energy Physics, 2017, 1683075.
 Lebed, A. G. (2016). Breakdown of the equivalence between active gravitational mass and energy for a quantum body. Journal of Physics: Conference Series, 738, 012036.
 Lebed, A. G. (2016). NonFermiliquid magic angle effects in high magnetic fields. Physical Review B, 94, 035162.
 Lebed, A. G. (2016). Possible existence of superconductivity in the quasionedimensional conductor Li0.9Mo6O17 at ultrahigh magnetic fields (H ≥ 45 T). Physical Review B, 93, 094523.
 Lebed, A. G. (2015). Breakdown of the equivalence between gravitational mass and energy for a quantum body: Theory and suggested experiments. International Journal of Modern Physics D, 24, 15300271  153002723.
 Lebed, A. G. (2015). NonFermiLiquid Crossovers in a QuasiOneDimensional Conductor in a Tilted Magnetic Field. Physical Review Letters, 115, 1570011  1570015.
 Lebed, A. G., & Sepper, O. (2015). Quantum limit and reentrant superconducting phases in the Q1D conductor Li(0.9)Mo(6)O(17). Physica B, 460, 231235.
 Lebed, A. G. (2014). Breakdown of the equivalence between gravitational mass and energy for a composite quantum body. Journal of Physics: Conference Series, 490(1).More infoAbstract: The simplest quantum composite body, a hydrogen atom, is considered in the presence of a weak external gravitational field. We define an operator for the passive gravitational mass of the atom in the postNewtonian approximation of the general relativity and show that it does not commute with its energy operator. Nevertheless, the equivalence between the expectation values of the mass and energy is shown to survive at a macroscopic level for stationary quantum states. Breakdown of the equivalence between passive gravitational mass and energy at a microscopic level for stationary quantum states can be experimentally detected by studying unusual electromagnetic radiation, emitted by the atoms, supported by and moving in the Earth's gravitational field with constant velocity, using spacecraft or satellite. © Published under licence by IOP Publishing Ltd.
 Lebed, A. G. (2014). Does the equivalence between gravitational mass and energy survive for a composite quantum body?. Advances in High Energy Physics, 2014.More infoAbstract: We define passive and active gravitational mass operators of the simplest composite quantum body  a hydrogen atom. Although they do not commute with its energy operator, the equivalence between the expectation values of passive and active gravitational masses and energy is shown to survive for stationary quantum states. In our calculations of passive gravitational mass operator, we take into account not only kinetic and Coulomb potential energies but also the socalled relativistic corrections to electron motion in a hydrogen atom. Inequivalence between passive and active gravitational masses and energy at a macroscopic level is demonstrated to reveal itself as timedependent oscillations of the expectation values of the gravitational masses for superpositions of stationary quantum states. Breakdown of the equivalence between passive gravitational mass and energy at a microscopic level reveals itself as unusual electromagnetic radiation, emitted by macroscopic ensemble of hydrogen atoms, moved by small spacecraft with constant velocity in the Earth's gravitational field. We suggest the corresponding experiment on the Earth's orbit to detect this radiation, which would be the first direct experiment where quantum effects in general relativity are observed. © 2014 A. G. Lebed.
 Lebed, A. G., & Sepper, O. (2014). Possible restoration of superconductivity in the quasionedimensional conductor Li0.9Mo6O17 in pulsed high magnetic fields H = 100 T. Physical Review B, 90, 094509.
 Lebed, A. G., & Sepper, O. (2014). Quantum limit in a magnetic field for triplet superconductivity in a quasionedimensional conductor. Physical Review B.
 Lebed, A. G. (2013). Is gravitational mass of a composite quantum body equivalent to its energy?. Central European Journal of Physics, 11(8), 969976.More infoAbstract: We define passive gravitational mass operator of a hydrogen atom in the postNewtonian approximation of general relativity and show that it does not commute with energy operator, taken in the absence of gravitational field. Nevertheless, the equivalence between the expectation values of passive gravitational mass and energy is shown to survive for stationary quantum states. Inequivalence between passive gravitational mass and energy at a macroscopic level results in time dependent oscillations of the expectation values of passive gravitational mass for superpositions of stationary quantum states, where the equivalence restores after averaging over time. Inequivalence between gravitational mass and energy at a microscopic level reveals itself as unusual electromagnetic radiation, emitted by the atoms, supported and moved in the Earth gravitational field with constant velocity using spacecraft or satellite, which can be experimentally measured. © 2013 Versita Warsaw and SpringerVerlag Wien.
 Lebed, A. G., & Sepper, O. (2013). Possible triplet superconductivity in the quasionedimensional conductor Li_{0.9}Mo_{6}O_{17}. Physical Review B  Condensed Matter and Materials Physics, 87(10).More infoAbstract: We consider a theoretical problem of the upper critical magnetic field parallel to a conducting axis of a quasionedimensional layered superconductor. We show that the orbital effects against superconductivity in a magnetic field are capable of destroying the superconducting phase at low temperatures if the interplane distance is less than the corresponding coherence length. Applications of our results to recent experiments, performed in the superconductor Li0.9Mo6O17, provide strong arguments in favor of a triplet superconducting pairing in this quasionedimensional layered conductor. © 2013 American Physical Society.
 Sepper, O., & Lebed, A. G. (2013). Nodeless versus nodal scenarios of possible triplet superconductivity in the quasionedimensional layered conductor Li_{0.9}Mo_{6}O _{17}. Physical Review B  Condensed Matter and Materials Physics, 88(9).More infoAbstract: We consider the problem of the orbital upper critical magnetic field, parallel to the most conducting axis of a quasionedimensional layered superconductor. It is shown that superconductivity can be destroyed through orbital effects at fields much higher than the socalled ClogstonChandrasekhar paramagnetic limiting field Hp, provided that superconducting pairing of electrons are of a triplet nature. We demonstrate that the superconducting state of the quasionedimensional layered conductor Li0.9Mo 6O17 is well described by the suggested theory. To this end, we consider two competing scenarios: (1) a superconducting order parameter without zeros on the Fermi surface, and (2) one with zeros on the Fermi surface  both are shown to lead to destruction of superconductivity at a magnetic field Hc2x, five times higher than Hp. With recent experimental measurements on the Li0.9Mo6O17 favoring the nodeless order parameter, we present a strong argument supporting triplet pairing in this compound. © 2013 American Physical Society.
 Lebed, A. G. (2012). DWavelike nodal superconductivity in the organic conductor (TMTSF) _{2}ClO _{4}. Physica B: Condensed Matter, 407(11), 18031805.More infoAbstract: We suggest theoretical explanation of the high upper critical magnetic field, perpendicular to conducting chains, Hc2 b′, experimentally observed in the superconductor (TMTSF) 2ClO 4, in terms of singlet superconducting pairing. In particular, we compare the results of dwavelike nodal, dwavelike nodeless, and swave scenarios of superconductivity. We show that, in dwavelike nodal scenario, superconductivity can naturally exceed both the orbital upper critical magnetic field and ClogstonShandrasekhar paramagnetic limit as well as reach experimental value, Hc2 b′≃6T, in contrast to dwavelike nodeless and swave scenarios. In our opinion, the obtained results are strongly in favor of dwavelike nodal superconductivity in (TMTSF) 2ClO 4, whereas, in a sister compound, (TMTSF) 2PF 6, we expect either the existence of triplet order parameter or the coexistence of triplet and singlet order parameters. © 2012 Elsevier B.V. All rights reserved.
 Lebed, A. G. (2012). GinzburgLandau slopes of the anisotropic upper critical magnetic field and band parameters in the superconductor (TMTSF) _{2}ClO _{4}. JETP Letters, 94(9), 689692.More infoAbstract: We theoretically determine the GinzburgLandau slopes of the anisotropic upper critical magnetic field in a quasionedimensional superconductor and correct the previous works on this issue. By using the experimentally measured values of the GinzburgLandau slopes in the superconductor (TMTSF)ClO 4, we determine band parameters of its electron spectrum. Our main result is that the socalled quantum dimensional crossover has to happen in this material in magnetic fields, H = 38 T, which are much lower than the previously assumed. We discuss how this fact influences metallic and superconducting properties of the (TMTSF) 2ClO 4. © 2011 Pleiades Publishing, Ltd.
 Lebed, A. G., & Sepper, O. (2012). Nonanalytical angular dependence of the upper critical magnetic field in a quasionedimensional superconductor. JETP Letters, 96(3), 176180.More infoAbstract: We have derived the socalled gap equation, which determines the upper critical magnetic field, perpendicular to conducting chains of a quasionedimensional superconductor. By analyzing this equation at low temperatures, we have found that the calculated angular dependence of the upper critical magnetic field is qualitatively different than that in the socalled effective mass model. In particular, our theory predicts a nonanalytical angular dependence of the upper critical magnetic field, H c2(0)  H c2(α) ~ α 3/2, when magnetic field is close to some special crystallographic axis and makes an angle α with it. We discuss possible experiments on the superconductor (DMET) 2I 3 to discover this nonanalytical dependence. © 2012 Pleiades Publishing, Ltd.
 Lebed, A. G. (2011). GinzburgLandau Slopes of the Anisotropic Upper Critical Magnetic Fields and Band Parameters in the Superconductor (TMTSF)2ClO4. JETP Letters.
 Lebed, A. G. (2011). Hidden reentrant and LarkinOvchinnikovFuldeFerrell superconducting phases in a magnetic field in a (TMTSF)_{2}ClO_{4}. Physical Review Letters, 107(8).More infoAbstract: We solve a longstanding problem about a theoretical description of the upper critical magnetic field, parallel to conducting layers and perpendicular to conducting chains, in a (TMTSF)2ClO4 superconductor. In particular, we explain why the experimental upper critical field, Hc2b ′6T, is higher than both the quasiclassical upper critical field and the Clogston paramagnetic limit. We show that this property is due to the coexistence of the hidden reentrant and LarkinOvchinnikovFuldeFerrell phases in a magnetic field in the form of three plane waves with nonzero momenta of the Cooper pairs. Our results are in good qualitative and quantitative agreement with the recent experimental measurements of Hc2b′ and support a singlet dwavelike scenario of superconductivity in (TMTSF) 2ClO4. © 2011 American Physical Society.
 Lebed, A. G. (2011). Hidden reentrant superconducting phase in a magnetic field in (TMTSF)_{2}ClO_{4}. JETP Letters, 94(5), 382385.More infoAbstract: We suggest explanation of the high upper critical magnetic field, perpendicular to conducting chains and parallel to conducting layers Hc2b'≃ 6 T, experimentally observed in the organic superconductor (TMTSF)2ClO4. In particular, we show that Hc2b' can be higher than both the quasiclassical upper critical field and ClogstonChandrasekhar paramagnetic limit in a singlet quasionedimensional superconductor. We predict the coexistence of the hidden Reentrant and LarkinOvchinnikovFuldeFerrell phases in a magnetic field. Our results are compared to the recent experimental data and shown to be in a good agreement with the experiments. © 2011 Pleiades Publishing, Ltd.
 Lebed, A. G. (2010). Universal fieldinduced spindensitywave phases: Theory versus experiment. Physica B: Condensed Matter, 405(11 SUPPL.), S106S107.More infoAbstract: We suggest a universal theory of the fieldinduced spindensitywave phase diagrams, experimentally observed in (TMTSF) 2X conductors. In particular, we show that, in layered quasionedimensional conductors, the critical magnetic fields ratios, H 1/H 0 = 0.73, H 2/H 0 = 0.59, and H 3/H 0 =0.49, are universal and do not depend on any fitting parameter. The suggested theory is in a good qualitative and quantitative agreement with the existing experimental data. © 2010 Elsevier B.V. All rights reserved.
 Lebed, A. G., & Si, W. u. (2010). LarkinOvchinnikovFuldeFerrell phase in the superconductor (TMTSF) _{2} ClO_{4}: Theory versus experiment. Physical Review B  Condensed Matter and Materials Physics, 82(17).More infoAbstract: We consider a formation of the LarkinOvchinnikovFuldeFerrell (LOFF) phase in a quasionedimensional (Q1D) conductor in a magnetic field, parallel to its conducting chains, where we take into account both the paramagnetic spin splitting and orbital destructive effects against superconductivity. We show that, due to a relative weakness of the orbital effects in a Q1D case, the LOFF phase appears in (TMTSF)2 ClO4 superconductor for real values of its Q1D band parameters. We compare our theoretical calculations with the recent experimental data by Y. Maeno's group and show that there is a good qualitative and quantitative agreement between the theory and experimental data. © 2010 The American Physical Society.
 Si, W. u., & Lebed, A. G. (2010). Unification theory of angular magnetoresistance oscillations in quasionedimensional conductors. Physical Review B  Condensed Matter and Materials Physics, 82(7).More infoAbstract: We present a unification theory of angular magnetoresistance oscillations, experimentally observed in quasionedimensional organic conductors, by solving the Boltzmann kinetic equation in the extended Brillouin zone. We find that, at commensurate directions of a magnetic field, resistivity exhibits strong minima. In two limiting cases, our general solution reduces to the results, previously obtained for the Lebed Magic Angles and LeeNaughtonLebed oscillations. We demonstrate that our theoretical results are in good qualitative and quantitative agreement with the existing measurements of resistivity in (TMTSF) 2 ClO4 conductor. © 2010 The American Physical Society.
 Lebed, A. G. (2009). Universal FieldInduced ChargeDensityWave Phase Diagram: Theory versus Experiment. Physical Review Letters, 103(4).More infoAbstract: We suggest a theory of fieldinduced chargedensitywave phases, generated by high magnetic fields in quasilowdimensional conductors. We demonstrate that, in layered quasionedimensional conductors, the corresponding critical magnetic field ratios are universal and do not depend on any fitting parameter. In particular, we find that H1/H0=0.73, H2/H0=0.59, H3/H0=0.49, and H4/H0=0.42, where Hn is a critical field of a phase transition between the fieldinduced chargedensitywave phases with numbers n and n+1. The suggested theory is in very good qualitative and quantitative agreement with the existing experimental data in α(ET)2KHg(SCN)4 material. © 2009 The American Physical Society.
 Lebed, A. G., & Wu, S. (2009). Supercrystalline phase in quasionedimensional conductors. Physica B: Condensed Matter, 404(34), 347349.More infoAbstract: A model, where phase transition between the Peierls and periodic soliton wall superlattice (supercrystalline) chargedensitywave phases occur in a magnetic field, is proposed. The model accounts for the peculiarities of the phase diagram in a quasionedimensional conductor (Per)2Pt(mnt)2. In the absence of a magnetic field, our model is equivalent to the exactly solvable model of Brazovskii, Dzyaloshinskii, and Kirova. © 2008 Elsevier B.V. All rights reserved.
 Si, W. u., & Lebed, A. G. (2009). Soliton wall superlattice chargedensitywave phase in the quasionedimensional conductor (Per) 2 Pt (mnt) 2. Physical Review B  Condensed Matter and Materials Physics, 80(3).More infoAbstract: We demonstrate that the Pauli spinsplitting effects in a magnetic field improve nesting properties of a realistic quasionedimensional electron spectrum. As a result, a high resistance Peierls chargedensitywave (CDW) phase is stabilized in high enough magnetic fields in (Per) 2 Pt (mnt) 2 conductor. We show that, in low and very high magnetic fields, the Pauli spinsplitting effects lead to a stabilization of a soliton wall superlattice (SWS) CDW phase, which is characterized by periodically arranged soliton and antisoliton walls. We suggest experimental studies of the predicted firstorder phase transitions between the Peierls and SWS phases to discover a unique SWS phase. It is important that, in the absence of a magnetic field and in a limit of very high magnetic fields, the suggested model is equivalent to the exactly solvable model of Brazovskii, Dzyaloshinskii, and Kirova for the SuSchriefferHeeger solitons. © 2009 The American Physical Society.
 Dutta, O., & Lebed, A. G. (2008). Cooper pairs with broken timereversal, parity, and spinrotational symmetries in singlet typeII superconductors. Physical Review B  Condensed Matter and Materials Physics, 78(22).More infoAbstract: We show that singlet superconductivity in the Abrikosov vortex phase is absolutely unstable with respect to the appearance of a chiral triplet component of a superconducting order parameter. This chiral component p x+ipy breaks timereversal, parity, and spinrotational symmetries of the internal order parameter responsible for a relative motion of two electrons in the Cooper pair. We demonstrate that the symmetrybreaking Pauli paramagnetic effects can be tuned by a magneticfield strength and direction and can be made of the order of unity in organic and hightemperature layered superconductors. © 2008 The American Physical Society.
 Lebed, A. G. (2008). Paramagnetic intrinsic Meissner effect in a bulk. JETP Letters, 88(3), 201204.More infoAbstract: We calculate the free energy of a quasitwodimensional (Q2D) superconductor with ξ⊥ < d in a parallel magnetic field, where ξ⊥ is a perpendicular to the conducting layer coherence length and d is the interlayer distance. It is shown to be different from that in the famous LawrenceDoniach model. In particular, at high enough magnetic fields, the Meissner currents are found to create an unexpected paramagnetic moment due to the shrinking of the Cooper pairs "sizes" in a direction perpendicular to the conducting layers. We suggest measuring this paramagnetic intrinsic Meissner effect in Q2D superconductors and superconducting superlattices. © 2008 Pleiades Publishing, Ltd.
 Lebed, A. G. (2008). Paramagnetic intrinsic Meissner effect in layered superconductors. Physical Review B  Condensed Matter and Materials Physics, 78(1).More infoAbstract: Free energy of a layered superconductor with ξ
 Lebed, A. G., & Si, W. u. (2007). Soliton wall superlattice in the quasionedimensional conductor (Per)2Pt(mnt)2. Physical Review Letters, 99(2).More infoAbstract: We suggest a model to explain the appearance of a high resistance high magnetic field chargedensitywave (CDW) phase, discovered by Graf et al. in (Per)2Pt(mnt)2, where Per is perylene and mnt is maleonitriledithiolate molecules. In particular, we show that the Pauli spinsplitting effects improve the nesting properties of a realistic quasionedimensional electron spectrum and, therefore, a high resistance Peierls CDW phase is stabilized in high magnetic fields. In low and very high magnetic fields, a periodic soliton wall superlattice (SWS) phase is found to be a ground state. We suggest experimental studies of the predicted phase transitions between the Peierls and SWS CDW phases in (Per)2Pt(mnt)2 to discover a unique SWS phase. © 2007 The American Physical Society.
 Lebed, A. G., & Wu, S. (2007). Soliton wall superlattice chargedensitywave phase in a magnetic field. JETP Letters, 86(2), 135138.More infoAbstract: A model where phase transitions between the Peierls and periodic soliton wall superlattice (SWS) chargedensitywave phases occur in a magnetic field is proposed. The model accounts for the peculiarities of the electron spectrum in a quasionedimensional conductor (Per)2Pt(mnt)2. Possible experimental investigations of the theoretically predicted phase transitions in (Per)2Pt(mnt)2 to discover a unique SWS phase are discussed. © 2007 Pleiades Publishing, Ltd.
 Ha, H. I., Lebed, A. G., & Naughton, M. J. (2006). Interference effects due to commensurate electron trajectories and topological crossovers in (TMTSF) 2 ClO4. Physical Review B  Condensed Matter and Materials Physics, 73(3).More infoAbstract: We report angledependent magnetoresistance measurements on (TMTSF) 2 ClO4 that provide strong support for a macroscopic quantum phenomenon, the "interference commensurate" (IC) effect, in quasione dimensional metals. In addition to observing rich magnetoresistance oscillations, and fitting them with oneelectron calculations, we observe a clear demarcation of fielddependent behavior at local resistance minima and maxima (versus field angle). Anticipated by a theoretical treatment of the IC effect in terms of Bragg reflections in the extended Brillouin zone, this behavior results from onedimensional → two dimensional (1D→2D) topological crossovers of electron wave functions as a function of field orientation. © 2006 The American Physical Society.
 Lebed, A. G. (2006). Cooper pairs with broken parity and spinrotational symmetries in dwave superconductors. Physical Review Letters, 96(3).More infoAbstract: Paramagnetic effects are shown to result in the appearance of a triplet component of order parameter in a vortex phase of a dwave superconductor in the absence of impurities. This component, which breaks parity and spinrotational symmetries of Cooper pairs, is expected to be of the order of unity in a number of modern superconductors such as organic, high Tc, and some others. A generic phase diagram of such typeIV superconductors, which are singlet ones at H=0 and in the Meissner phase, and characterized by singlettriplet mixed Copper pairs Δs+iΔt with broken symmetries in a vortex phase, is discussed. © 2006 The American Physical Society.
 Lebed, A. G. (2006). TypeIV superconductivity: Can superconductivity be more exotic than unconventional?. Journal of Low Temperature Physics, 142(34), 173178.More infoAbstract: Abrikosov vortex phase in swave layered superconductor in a parallel magnetic field is shown to be absolutely unstable with respect to the appearance of a triplet component which breaks inversion (parity) and spinrotational symmetries of Cooper pairs. Symmetry breaking paramagnetic effects are demonstrated to be of the order of unity if the orbital upper critical field, H c2 (0), is of the order of Clogston paramagnetic limiting field, H p. We suggest a generic phase diagram of such typeIV superconductor, which is singlet one at H=0 and in the Meissner phase and characterized by mixed singlettriplet order parameter with broken symmetries of Copper pairs in vortex phase. A possibility to observe typeIV superconductivity in clean organic, highTc, and MgB 2 superconductors is discussed. © Springer Science+Business Media, Inc 2006.
 Lebed, A. G., & Bagmet, N. N. (2006). Quantum (nanoscale) limit in a parallel magnetic field in layered Q1D conductors. Journal of Low Temperature Physics, 142(34), 499502.More infoAbstract: We show that electron wave functions in a quasionedimensional (Q1D) layered conductor in a parallel magnetic field are always localized on conducting layers. Wave functions and electron spectrum in a quantum limit, where the "sizes" of quasiclassical electron orbits are of the order of nanoscale distances between the layers, are determined. Possible applications of our results to physical properties of Q1D materials in their superconducting and metallic phases are discussed. © 2007 Springer Science+Business Media, Inc.
 Yoshino, H., Bayindir, Z., Roy, J., Shaw, B., Ha, H., Lebed, A. G., & Naughton, M. J. (2006). Pulsed field studies of angular dependence of unconventional magnetoresistance in (TMTSF)_{2}ClO_{4}. AIP Conference Proceedings, 850, 15421543.More infoAbstract: The field and angle dependence of magnetoresistance of (TMTSF) 2ClO4 was studied by a pulsed magnetic field system up to 40 T. The third angular effect of this quasionedimensional metal was clearly observed as well as LeeNaughton oscillations with small amplitude for abplane rotation of the magnetic field. Saturating behavior of the field dependence of the magnetoresistance at a local minimum of the angular dependence contrasts with nonsaturation (or divergence) at general field orientations to the crystal. This unconventional behavior may be explained by crossover of electronic system from one to twodimensional suggested by recent theories based on quantum mechanics. © 2006 American Institute of Physics.
 Yoshino, H., Bayindir, Z., Roy, J., Shaw, B., Ha, H., Lebed, A., & Naughton, M. J. (2006). Unconventional field dependence of magnetoresistance of (TMTSF) _{2}ClO _{4} studied by 46T pulsed magnetic field system. Journal of Low Temperature Physics, 142(34), 323326.More infoAbstract: The field and angle dependence of magnetoresistance of (TMTSF) measured by a pulsed magnetic field system up to 40 T at 4.2 K to investigate its behavior at high field limit. Two minima of magnetoresistance due to the third angular effect of quasionedimensional (Q1D) metals were successfully observed as well as LeeNaughton oscillations by sub xyplane rotation of the magnetic field. It was found that magnetoresistance tends to saturate at minima positions, while it generally diverges up to the highest magnetic field region. © Springer Science+Business Media, LLC 2006.
 Yoshino, H., Bayindir, Z., Roy, J., Show, B., Ha, H. ., Lebed, A. G., Naughton, M. J., Kikuchi, K., Nishikawa, H., & Murata, K. (2006). Pulsed magnetic field study of unconventional magnetoresistance of Q1D superconductors (TMTSF)_{2}ClO_{4}and (DMET)_{2}I _{3}. Journal of Physics: Conference Series, 51(1), 339342.More infoAbstract: Quasionedimensional (Q1D) organic conductors with simple open Fermi surfaces have provided novel angular dependent magnetoresistance oscillation (AMRO) phenomena for the last two decades. Both semiclassical and quantum mechanical theories well explain these phenomena, but detailed study of the field dependence probably gives a crucial test. Recently it was proposed that a kind of AMRO that is known as "LeeNaughton oscillations (LNO)" observed for (TMTSF)2ClO4 is a result of dimensional crossover of electronic system from oneto twodimension on changing the field orientation. We have studied the field dependence of the magnetoresistance of Q1D superconductors (TMTSF)2ClO4 and (DMET) 2I3by using a 46T pulsed magnetic field system and found the B1/2behavior at minima of LNO. © 2006 IOP Publishing Ltd.
 Lebed, A. G. (2005). Quantum limit in a parallel magnetic field in layered conductors. Physical Review Letters, 95(24).More infoAbstract: We show that electron wave functions in a quasitwodimensional conductor in a parallel magnetic field are always localized on conducting layers. In particular, wave functions and the electron spectrum in a quantum limit, where the sizes of quasiclassical electron orbits are of the order of nanoscale distances between the layers, are determined. ac infrared measurements to investigate Fermi surfaces and to test Fermiliquid theory in quasitwodimensional organic and highTc materials in high magnetic fields, Hâ‰1045T, are suggested. © 2005 The American Physical Society.
 Lebed, A. G. (2005). TypeIV superconductivity: Cooper pairs with broken inversion and timereversal symmetries in conventional superconductors. JETP Letters, 82(4), 204209.More infoAbstract: The vortex phase in a singlet superconductor in the absence of impurities is shown to be absolutely unstable with respect to the appearance of a triplet component that breaks both the inversion and timereversal symmetries of Cooper pairs. The symmetry breaking paramagnetic effects are demonstrated to be of the order of unity if the orbital upper critical field, Hc2(0), is of the order of the Clogston paramagnetic limiting field, Hp. We suggest a generic phase diagram of such a typeIV superconductor that is a singlet one at H = 0 and characterized by a mixed singlettriplet order parameter with broken timereversal symmetry in the vortex phase. The possibility to observe typeIV superconductivity in clean organic, highTc, MgB2, and other superconductors is discussed. © 2005 Pleiades Publishing, Inc.
 Lebed, A. G., Ha, H., & Naughton, M. J. (2005). Angular magnetoresistance oscillations in organic conductors. Physical Review B  Condensed Matter and Materials Physics, 71(13).More infoAbstract: We demonstrate that electron wave functions change their dimensionality at some commensurate directions of a magnetic field in conductors with open [quasionedimensional (Q1D)] sheets of Fermi surface. These 1D→2D dimensional crossovers lead to delocalization of wave functions and are responsible for angular magnetoresistance oscillations. As an example, we show that suggested theory is in qualitative and quantitative agreement with the recent experimental data obtained on (TMTSF)2 ClO4 conductor. © 2005 The American Physical Society.
 Lebed, A. G., Bagmet, N. M., & Naughton, M. J. (2004). Magic angles, AMRO and interference effects in layered conductors. Journal De Physique. IV : JP, 114, 7780.More infoAbstract: We analytically solve kinetic equation in the extended Brillouin zone and demonstrate that the interference effects which occur as electrons move along open orbits result in the appearance of Magic Angle (MA) minima of resistivity. A comparison of our theory with MA phenomena observed in resitivity component ρ⊥ (H, α), perpendicular to conducting layers in (TMTSF)2X and α (BEDTTTF)2MHg(SCN)4 conductors, shows a good qualitative agreement, including the first explanation why MA's with large indexes, N > 1, are observed in (TMTSF)2X (X = ClO4 and PF6) and α(BEDTTTF)2MHg(SCN) 4 compounds. Both physical meaning of the above mentioned interference effects and mathematical expressions for ρ⊥ (H, α) are different from that in a socalled OsadaÕs model. © EDP Sciences,.
 Lebed, A. G., Bagmet, N. N., & Naughton, M. J. (2004). Magic angle effects and angular magnetoresistance oscillations as dimensional crossovers. Physical Review Letters, 93(15), 15700611570064.More infoPMID: 15524929;Abstract: The effects of magic angle (MA) and magnetoresistance oscillations as dimensional crossovers, were investigated. The interference effects between velocity and density of states, which occur as electrons move along open orbits in the Brillouin zone in anisotropic conductors, were observed to change the dimensionality of wave function at MA directions. It was observed that 1D → 2D dimensional crossovers resulted in appearance of sharp minima. The results show that MA and angular magnetoresistance osciilations occurred due to the existence of quaionedimensional sheets of Fermi surface.
 Lebed, A. G. (2003). Theory of magnetic fieldinduced chargedensitywave phases. JETP Letters, 78(3), 138142.More infoAbstract: We elaborate an analytical theory of a cascade of magnetic fieldinduced chargedensitywave (FICDW) phases. It is shown that the following features distinguish it from the wellknown spindensitywave cascade: (1) the FICDW phases exist at temperatures much lower than the characteristic CDW transition temperature at H = 0; (2) the cascade of the FICDW phases dramatically changes at certain directions of a magnetic field due to an interplay of Zeeman spinsplitting and electron motion along open Fermi surfaces. Theoretical results are compared with the recent experimental attempts to reveal FICDW phases in the organic conductors α(ET)2MHg(SCN)4 (M = K, Tl, Rb, etc.). © 2003 MAIK "Nauka/Interperiodica".
 Lebed, A. G., & Naughton, M. J. (2003). Interference Commensurate Oscillations in QuasiOneDimensional Conductors. Physical Review Letters, 91(18), 18700311870034.More infoPMID: 14611308;Abstract: The angular magnetoresistance oscillations in quasionedimensional conductors were discussed. The origin of the oscillations were related to the interference effects resulting from Bragg reflections which occured as electrons move along quasiperiodic and periodic electron trajectories in the extended Brillouin zone. Two most genaral electron trajectories, characterised by θ and φ were considered which corresponded commensurate oscillations and generalized DannerKangChaikin (DKC). It was shown that the commensurate directions of a magnetic field corresponded to the minima at large enough φ whereas smaller minima occurred for only odd values of N depending in the particluar value of φ.
 Lebed, A. G. (2002). Fieldinduced spindensitywave phases in quasionedimensional conductors: Theory versus experiments. Physical Review Letters, 88(17), 17700111770014.More infoPMID: 12005777;Abstract: The fieldinduced spindensitywave phases (FISDW) were studied in quasionedimensional conductors. It was showed that the important features of the magnetic field inducedFISDW phase diagrams were missed by the quantized nesting model. It was speculated that the 3D quantum Hall effect (QHE) existed only in the quantum FISDW phases and disappeared in the quasiclassical FISDW states. It was expected that physical properties as a nonlinear FISDW conductivity and magic angle phenomenon were different in the quantum FISDW and quasiclassical FISDW phases.
 Lebed, A. G. (2002). Magnetic tests to reveal triplet supeconductivity in (TMTSF)_{2}PF_{6} and a possible breaking of a time reversal symmetry in Sr_{2}RuO_{4}, LBCO, and YBCO. International Journal of Modern Physics B, 16(2022), 3198.
 Lebed, A. G. (2002). Triplet superconductivity order parameter in an organic superconductor (TMTSF)_{2}PF_{6}. International Journal of Modern Physics B, 16(2022), 3271.
 Lebed, A. G., & Naughton, M. J. (2002). Fermi surface interference effects and angular magnetic oscillations in Q1D conductors. Journal De Physique. IV : JP, 12(9), Pr9/369Pr9/372.More infoAbstract: We have derived a common analytical expression to describe angular magnetic oscillations observed in quasionedimensional (Q1D) conductors (TMTSF)2X and (DMET)2I3. Among these are the Danner et al. oscillations, the "third angular effect", and very rich angular oscillations discovered by Lee et al. The physical meaning of the latter oscillations is shown to be related to interference effects.
 Lebed, A. G. (2000). Does the "quantized nesting model" properly describe the magneticfieldinduced spindensitywave transitions?. JETP Letters, 72(3), 141143.More infoAbstract: Theoretical reinvestigation of a socalled fieldinduced spindensitywave (FISDW) phase diagram in a magnetic field in quasionedimensional compounds (TMTSF)2X (X = PF6, ClO4, AsF6, etc.) has revealed some novel qualitative features. Among them are (1) the FISDW wave vector is never strictly quantized; and (2) the FISDW phase diagram consists of two regions: (a) "Quantum FISDW," where there exist jumps of the FISDW wave vectors between different FISDW subphases and (b) "Quasiclassical FISDW," where the jumps disappear above some critical points and only one FISDW phase (characterized by a wave vector oscillating with a magnetic field) exists. Both these features are due to taking account of the breaking of an electronhole symmetry. They contradict the previous textbook theoretical results (including the calculations of the "Three Dimensional Quantum Hall Effect") performed by means of the "Quantized Nesting Model" which explicitly assumes the existence of the electronhole symmetry. We stress that some effects related to the phenomena described above were experimentally observed but not properly interpreted. © 2000 MAIK "Nauka/Interperiodica".
 Lebed, A. G. (2000). Possible triplet order parameter in a Q1D organic superconductor (TMTSF)_{2}PF_{6}. Physica C: Superconductivity and its Applications, 341348(PART 2), 16991700.More infoAbstract: We point out that (TMTSF)2PF6 compound at P ≃ 6 kbar is possibly a triplet superconductor with the vector order parameter d = (dx ≠ 0, dy ,dz = 0). It corresponds to an anisotropic spin susceptibility in a superconducting state: χb′(z) = χ0, χa(x) ≠ χ0, where χ0 is its value in a metallic phase. (Here, the spin quantization axis, z, is parallel to the easy axis, b′, of an antiferromagnetic SDW phase existing at P = 0). It is shown that the suggested order parameter can explain why the upper critical field along b′axis (I.J. Lee, M.J. Naughton, G. Danner, and P.M. Chaikin, Phys. Rev. Lett. 78, 3555 (1997)) exceeds all paramagnetic limiting fields (including that for a nonuniform superconductivity) whereas the upper critical field along the aaxis is restricted by the Pauli paramagnetic effects. The triplet order parameter is consistent with the earlier results on a destruction of superconductivity by nonmagnetic impurities and the absence of the HebelSlichter peak in the NMR data as well as with the recent Knight shift measurements by S. Brown et al and by I. J. Lee et al. © 2000 Elsevier Science B.V. All rights reserved.
 Lebed, A. G., & Hayashi, N. (2000). Paramagneticlike destructive mechanism against superconductivity in Sr_{2}RuO_{4}: A triplet scenario versus a singlet one. Physica C: Superconductivity and its Applications, 341348(PART 2), 16771678.More infoAbstract: The most popular description of superconductivity phenomenon in Sr2RuO4 is based on a socalled singleband (usually γband) "isotropic pwave order parameter". In a magnetic field parallel to the conducting planes, such triplet "isotropic pwave phase" is not destroyed by the ClogstonChandrasekhar paramagnetic limiting field and can be destroyed only by the Meissner currents (i.e., the orbital effects). We analyze the orbital destructive effects against superconductivity for inplane magnetic field (when electron orbits are open) and find that Hc2∥(0) ≃ 0.75 Tc(dHc2∥(T)/dT)Tc (which is a little bigger than the WerthamerHelfandHohenberg value for an isotropic 3D case). We point out that the experimentally determined ratio Hc2∥(0)/Tc(dHc2∥(T)/dT)Tc ≃ 0.44  0.5 in Sr2RuO4 is significantly less than the calculated value 0.75. Since the upper critical field, Kc2∥(T). is a well experimentally defined quantity in Sr2RuO4 (unlike highTc superconductors) we conclude that the singleband triplet "isotropic pwave order parameter" seems to be inappropriate description of superconductivity in this material. Two possibilities are discussed: 1) Threeband nature of triplet superconductivity; 2) Singlet (dwave) nature of superconducting pairing (in this case, the destructive actions of both the orbital effects and the ClogstonChandrasekhar paramagnetic effects result in an agreement with the experimentally observed value of Hc2∥(0)/Tc(dHc2∥(T)/dT)Tc). © 2000 Elsevier Science B.V. All rights reserved.
 Lebed, A. G., Machida, K., & Ozaki, M. (2000). Triplet electron pairing and anisotropic spin susceptibility in organic superconductors (TMTSF)_{2}X. Physical Review B  Condensed Matter and Materials Physics, 62(2), R795R798.More infoAbstract: We argue that the (TMTSF)2PF6 compound under pressure is likely a triplet superconductor with a vector order parameter d(k)=(da(k)≠0, dc(k)=?, d′(k)=0); da(k)>dc(k). It corresponds to an anisotropic spin susceptibility at T=0: χb′=χ0, χa≪χ0, where χ0 is its value in a metallic phase. (The spinquantization axis, z, is parallel to a socalled b′ axis.) We show that the suggested order parameter explains why the upper critical field along the b′ axis exceeds all paramagnetic limiting fields, including that for a nonuniform superconducting state, whereas the upper critical field along the a axis (a⊥b′) is limited by the Pauli paramagnetic effects [I. J. Lee, M. J. Naughton, G. M. Danner, and P. M. Chaikin, Phys. Rev. Lett. 78, 3555 (1997)]. The triplet order parameter is in agreement with the recent Knight shift measurements by I. J. Lee et al. as well as with the early results on a destruction of superconductivity by nonmagnetic impurities and on the absence of the HebelSlichter peak in the NMR relaxation rate. ©2000 The American Physical Society.
 Lebed, A. G. (1999). Gap symmetry and a revival of superconductivity in high parallel magnetic fields in Q2D and Q1D organic, highT_{c}, and Sr_{2}RuO _{4} compounds. Journal of Superconductivity and Novel Magnetism, 12(3), 453458.More infoAbstract: From the BCS theory, we derive an equation determining the upper critical field, Hc2(T), parallel to conducting planes of both layered Q2D and Q1D superconductors. It extends the quasiclassical GinzburgLandauAbrikosov Gor'kov (GLAG) and LawrenceDoniach descriptions of Hc2(T) to the case of high magnetic fields where the quantum nature of an electron motion along open Fermi surfaces is important. This equation demonstrates two new phenomena: (1) a complete restoration of superconductivity at H ≃ H c5 > Hc2(0) in the case of pwave pairing of electrons; (2) a surviving of superconductivity at Hc2(0) < H < H p* in the case of s(d)wave pairing, where Hp* ≠ Hp [Here, Hc2(0) and Hp are the quasiclassical GLAG upper critical field and the paramagnetic ClogstonChandrasekhar limiting field, correspondingly; Hc5 and Hp* are defined in the text]. Our analysis of recent experimental data on (TMTSF)2PF6 by I. J. Lee et al. and M. J. Naughton et al. shows that superconductivity significantly exceeds H p*. This demonstrates a strong suppression of the Pauli pairbreaking effects and may reflect a pwave pairing of electrons. We propose to measure Hc2(T) in Sr2RuO4 (which is believed to be a pwave superconductor) to prove a symmetry of a superconducting order parameter. © 1999 Plenum Publishing Corporation.
 Lebed, A. G. (1999). Revival of superconductivity in high magnetic fields and a possible pwave pairing in (TMTSF)_{2}PF_{6}. Physical Review B  Condensed Matter and Materials Physics, 59(2), R721R724.More infoAbstract: From the BCS theory, we derive an equation which accounts for quantum effects of an electron motion along open Fermi surfaces and determines the upper critical field Hc2⊥(T) perpendicular to the chains of a quasionedimensional conductor. This equation demonstrates two unusual phenomena: (1) restoration of superconductivity at H>Hc2⊥(0) in pwave superconductors, where Hc2⊥(0) is the quasiclassical upper critical field; (2) surviving of superconductivity at Hc2⊥(0), Hp
 Lebed, A. G., & Yamaji, K. (1998). Restoration of superconductivity in high parallel magnetic fields in layered superconductors. Physical Review Letters, 80(12), 26972700.More infoAbstract: We derive an equation determining the upper critical field Hc2∥(T) parallel to conducting planes of a layered superconductor from the BCS theory. It extends the descriptions of Hc2∥(T) within the GinzburgLandauAbrikosovGor'kov theory and the LawrenceDoniach model to the case of strong magnetic fields. From this equation, it follows that orbital effects of an electron motion along an open Fermi surface in a magnetic field start to restore superconductivity at magnetic fields higher than the quasiclassical upper critical field and result in the appearance of a reentrant phase with Tc(H) ≃ Tc(0). A stability of the reentrant phase against fluctuations is discussed.
 Lebed, A. G. (1997). Ground state of (TMTSF)_{2}ClO_{4} in high magnetic fields: The creation of SuSchriefferHeeger solitons. Physical Review B  Condensed Matter and Materials Physics, 55(3), 12991302.More infoAbstract: It is shown that the problem of spindensitywave formation in a quasionedimensional organic conductor (TMTSF)2ClO4 in a magnetic field is equivalent to BrazovskiiDzyaloshinskiiKirova variant of an exactly solvable onedimensional problem of SuSchriefferHeeger (SSH) solitons. We demonstrate that the ground state in (TMTSF)2ClO4 in high magnetic fields corresponds to SSH solitonic superstructure. We calculate the magnetic moment and energy gap in an electron spectrum and discuss recent experimental data in terms of the creation of SSH solitonic superstructure.
 Lebed, A. G. (1997). New aspects of nonFermiliquid behaviour in Q1D metals. Synthetic Metals, 85(13), 16151616.More infoAbstract: The second order corrections to magnetic moment, M, magnetic susceptibility, χ, and specific heat, C, due to electronelectron ("ee") interactions are calculated in a Q1D conductor (TMTSF)2ClO4 in a metallic phase. Strong magnetic oscillations of these thermodynamical quantities are found to exist due to the oscillations of matrix elements of "ee" interactions in the Peierls channel under the condition of magnetic breakdown. We note that the frequency of the oscillations corresponds to open ("interference") orbits that contradicts Fermi liquid description of quasiparticles. We demonstrate that the relative magnitudes of these forbidden oscillations are anomalously large: δχ/χ0 ∼ 1  10, δM/M0 ∼ 101, and δC/C0 ∼ 102.
 Lebed, A. G., & Bagmet, N. M. (1997). Nonanalytical magnetoresistance and a new method of investigation of Fermi surfaces in Q2D and Q1D conductors. Synthetic Metals, 85(13), 14931494.More infoAbstract: We demonstrate that transverse magnetoresistance is a nonanalytical function of a magnetic field, ρ⊥ ∼ H1/2, if a magnetic field is normal to quasitwodimensional (Q2D) Fermi surface (FS) at an inflexion point. Recently discovered OsadaKagoshima angular resonance is described in terms of the existence of an inflexion point on the FS of (TMTSF)2ClO4conductor. It is shown that at arbitrary direction of a magnetic field in a 2D plane transverse magnetoresistance does not depend on electron relaxation time and obeys a linear law, ρ⊥ ∼ AH, where A depends on some local characteristics of a Q2D FS. The above mentioned effects provide us with a new method of investigation of FS's in strongly anisotropic Q2D (Q1D) conductors.
 Lebed, A. G., & Bagmet, N. N. (1997). Nonanalytical magnetoresistance, the third angular effect, and a method to investigate Fermi surfaces in quasitwodimensional conductors. Physical Review B  Condensed Matter and Materials Physics, 55(14), R8654R8657.More infoAbstract: We demonstrate that transverse magnetoresistance is a nonanalytical function of the magnetic field, ρ⊥(H)∼H1/2, if a magnetic field is parallel to the plane of anisotropy and normal to the Fermi surface at an inflection point in a quasitwodimensional (Q2D) conductor. The socalled "third angular effect," recently discovered in organic conductors (TMTSF)2X (X=ClO4,PF6) and (DMET)2I3, is interpreted in terms of the existence of an inflection point on their Fermi surfaces. Nonanalytical magnetoresistance is predicted to appear when the magnetic field is applied at the "third magic angles," Θ=±Θc. It is also shown that at arbitrary directions of the inplane magnetic field the magnetoresistance does not depend on relaxation time and obeys the law ρ⊥(H)∼AH with factor A being a function of local characteristics of a Q2D Fermi surface. The abovementioned phenomena provide useful methods to investigate Fermi surfaces in strongly anisotropic Q2D conductors including organic and highTc superconductors.
 Lebed, A. G., & Yamaji, K. (1997). Restoration of superconductivity at high magnetic fields in layered highT_{c} and organic superconductors. Physica C: Superconductivity and its Applications, 282287(PART 3), 18591860.More infoAbstract: An integral equation determining the upper critical field parallel to the conducting plane of a layered superconductor is derived from microscopic BCS theory. From this equation, it follows that the superconductivitydestruction mechanism due to the orbital effect becomes ineffective at magnetic fields higher than a critical field Hc4 due to a quantum nature of an electron motion in a magnetic field. This leads to the appearance of reentrant superconducting phase with dTc/dH > 0 in the case of ppairing and under certain conditions in the case of s(d)pairing. We also show that the orbital effect cannot destroy superconductivity at T = 0 at arbitrary magnetic fields. Therefore qualitative deviations from the description of GLAG (WHH) theory have to appear for arbitrary symmetry of the order parameter at low enough temperatures. We argue that p(s)wave superconductor Sr2RuO4 as well as s(d)wave superconductors TlBa2CaCu2O7, Tl2Ba2Ca3Cu4Ox, β(ET)2AuI2, and κ(ET)2I3 are good candidates for the observation of the above mentioned phenomena.
 Sasaki, T., Lebed, A. G., Fukase, T., & Toyota, N. (1997). Magnetic field response of the spin density wave in α(BEDTTTF)_{2}KHg(SCN)_{4}. Synthetic Metals, 86(1 3 pt 3), 20632064.More infoAbstract: Magnetic phase diagram and metal  spindensitywave (SDW) transition in an organic conductor α(BEDTTTF)2KHg(SCN)4 are revisited from a view point of magnetic torque measurements. The metal  SDW transition temperature determined by magnetic torque measurements shifts from about 8K at H = O T to higher temperatures with increasing magnetic field, and tends to be saturated. This transition line is different from that determined by the socalled kink structure of the magnetoresistance so far. Inside the SDW phase, an additional phase boundary exists at the temperature independent field of 23 T, where the effective mass and Dingle temperature determined by de Haas  van Alphen oscillations change their values.
 Sasaki, T., Lebed, A. G., Fukase, T., & Toyota, N. (1997). Magnetic field response of the spin density wave in α(BEDTTTF)_{2}KHg(SCN)_{4}. Synthetic Metals, 86(13), 20632064.More infoAbstract: Magnetic phase diagram and metal  spindensitywave (SDW) transition in an organic conductor α(BEDTTTF)2KHg(SCN)4 are revisited from a view point of magnetic torque measurements. The metal  SDW transition temperature determined by magnetic torque measurements shifts from about 8K at H = 0 T to higher temperatures with increasing magnetic field, and tends to be saturated. This transition line is different from that determined by the socalled kink structure of the magnetoresistance so far. Inside the SDW phase, an additional phase boundary exists at the temperature independent field of 23 T, where the effective mass and Dingle temperature determined by de Haas  van Alphen oscillations change their values.
 Lebed, A. G. (1996). Magnetic oscillations in a normal state of organic conductors: Manybody approach. Journal de Physique I, 6(12), 18191836.More infoAbstract: We argue that magnetic and angular oscillations observed in quasionedimensional (Q1D) organic conductors represent a new type of manybody phenomena. The physical nature of such effects as "magic angles" in (TMTSF)2ClO4, (TMTSF)2PF6, and (DMETTSeF)2 AuCl2 as well as "rapid magnetic oscillations" in (TMTSF)2ClO4 is shown to be beyond the standard theory of metals. Below we discuss an explanation of these phenomena which utilizes unusual manybody effect  a change of an effective dimensionality of electronelectron ("ee") interactions with changing both a magnitude and a direction of a magnetic field. We show that some exotic transport properties of a metallic state can be interpreted in terms of these dimensional crossovers. We also demonstrate that magnetic field dependence of "ee" interactions has to break Fermi liquid description of quasiparticles at high magnetic fields, H ≥ 25  30 T. This leads to the appearance of strong forbidden oscillations of magnetic susceptibility, δχ/χ0 ∼ 110, and magnetic moment, δM/M0 ∼ 0.1. All of the above mentioned unique properties of a metallic phase in (TMTSF)2X and (DMETTSeF)AuCl2 allow us to call it an anomalous metallic phase. © Les Éditions de Physique 1996.
 Sasaki, T., Lebed, A. G., Fukase, T., & Toyota, N. (1996). Interplay of the spindensitywave state and magnetic field in the organic conductor α(BEDTTTF)_{2}KHg(SCN)_{4}. Physical Review B  Condensed Matter and Materials Physics, 54(18), 1296912978.More infoAbstract: Magnetic phase diagram of a quasitwodimensional organic conductor α(BEDTTTF)2KHg(SCN)4 is revisited from a viewpoint of magnetic torque measurements in high fields up to 30 T. A phase boundary that is interpreted as a metalspin density wave (SDW) phase transition is found by using torque measurements. It is shown that this phase boundary is clearly distinguished from socalled kink transition of the magnetoresistance. We demonstrate that the transition temperature defined by the midpoint of the broad phase transition is almost independent on magnetic field up to 23 T. Onset temperature of the transition shifts from about 8 K at H=0T to higher temperatures with increasing of a magnetic field, and tends to be saturated. The onset line of this transition follows well the theoretical expectation that SDW has to be stabilized by a magnetic field. This allows us to estimate such important band parameters of the quasionedimensional section of the Fermi surface as an effective mass, mID≃(0.5±0.1)m0, and an upper limit of an imperfect nesting bandwidth tc′≃( 10 ± 1 ) K. The other phase boundaries determined by the position of the kink and hysteresis properties of the magnetoresistance are interpreted as subphases inside the SDW phase. Inside the SDW phase, we find an additional phase boundary at the temperatureindependent field of 23 T, which corresponds to the appearance of de Haasvan Alphen oscillations on a magnetic torque curve. At the 23 T boundary, both the effective mass, m*, and the Dingle temperature, TD, change their values from m*=(1.67 ± 0.05) m0 and TD=3.74.0 K in low magnetic field region to (1.95 ± 0.05) m0 and 2.52.8 K in high field region. The latter phenomenon is discussed in terms of a reconstruction of the Fermi surface due to the SDW formation. Hysteresis of the magnetoresistance observed in one of the subphases inside the SDW phase is studied in detail by measuring both the temperature and the magnetic field dependences.
 Gor'kov, L., & Lebed, A. G. (1995). Anion gap and stability of the metallic phase for (TMTSF)_{2}ClO_{4}. Synthetic Metals, 70(1 3 pt 2), 727730.More infoAbstract: Starting with the prototype nesting spectrum of (TMTSF)2PF6, it is emphasized that the gap due to anion ordering (AO) would result in a somewhat different SDW state for ClO4 if the 'antinesting' term, t′b, was omitted. The field then first diminishes that term, improving nesting. At the same time the field decreases pairing between subbands with nesting features because of the difference in the symmetry of their wavefunctions. This leads to the reentrance of the metallic state. The magnetic breakdown (MB) gradually decreases the effect of AO. Properties of the 'prototype' PF6material are expected to be seen again at large magnetic fields. However, it occurs in a peculiar phase diagram with sharp spikes in TSDW periodic in the inverse magnetic field, 1/H. Cyclotron resonance on open orbits is discussed to study whether the 'transverse' gap due to AO in (TMTSF)2ClO4 manifests itself in other properties.
 Gor'kov, L., & Lebed, A. G. (1995). Anion gap and stability of the metallic phase for (TMTSF)_{2}ClO_{4}. Synthetic Metals, 70(13), 727730.More infoAbstract: Starting with the prototype nesting spectrum of (TMTSF)2PF6, it is emphasized that the gap due to anion ordering (AO) would result in a somewhat different SDW state for ClO4 if the "antinesting" term, t′b, was omitted. The field then first diminishes that term, improving nesting. At the same time the field decreases pairing between subbands with nesting features because of the difference in the symmetry of their wavefunction. This leads to the reentrance of the metallic state. The magnetic breakdown (M B) gradually decreases the effect of AO. Properties of the "prototype" PF6material are expected to be seen again at large magnetic fields. However, it occurs in a peculiar phase diagram with sharp spikes in TSDW periodic in the inverse magnetic field, 1/H. Cyclotron resonance on open orbits is discussed to study whether the "transverse" gap due to AO in (TMTSF)2ClO4 manifests itself in other properties. © 1995.
 Gor'kov, L., & Lebed, A. G. (1995). Fast oscillations in the surface impedance of (TMTSF)2ClO4 in a magnetic field. Physical Review B, 51(2), 13621365.More infoAbstract: The energy gap due to anion ordering introduces essential differences for electrons of two particular subbands in a magnetic field. The magnetic breakdown restores the behavior of the prototype PF6 in an irregular manner as the field increases. The fast oscillations (periodic in 1/H) appear to be due to the fact that the electron trajectories in ClO4 coincide with those in PF6 only at specific values of H. The fast oscillations superimpose on the cyclotronresonancetype singularities. © 1995 The American Physical Society.
 Gorkov, L. P., & Lebed, A. G. (1995). Metalphase stability of (TMTSF)2ClO4 in high magnetic fields, where TMTSF is tetramethyltetraselenafulvalene. Physical Review B, 51(5), 32853288.More infoAbstract: The fieldinduced spindensitywave state in (TMTSF)2ClO4, where TMTSF is tetramethyltetraselenafulvalene, develops because the field diminishes the antinesting terms, tb, to restore the spindensity wave (SDW) that would exist at tb=0 despite the anion gap in ClO4. The gap changes the wave functions symmetry for nested subbandsone of them changes sign upon crossing the new zone boundary, destroying the coherence of paired electrons at H 0. Competition between the two phenomena leads to a reentrance of the metallic state. Magnetic breakdown is unable to restore a PF6type ground state and reveals itself in a pattern of peaks for TSDW(H) periodic in H1. © 1995 The American Physical Society.
 Lebed, A. G. (1995). Magic angles effects and rapid magnetic oscillations in organic superconductors. Synthetic Metals, 70(1 3 pt 2), 993996.More infoAbstract: In the framework of the quantum approach to electronelectron ('ee')·interactions in a magnetic field, two related phenomena, 'magic angles' and 'rapid magnetic oscillations', are investigated. We show that the sharp angular magnetoresistance dips have to exist at the main 'magic angles' in Q1D metals due to the unusual dependence of 'ee'  scattering on the direction of the magnetic field. We suggest that 'rapid magnetic oscillations' are the result of the influence of a magnetic breakdown on 'ee'scattering. Our calculations are in qualitative agreement with experimental data.
 Lebed, A. G. (1995). Magic angles effects and rapid magnetic oscillations in organic superconductors. Synthetic Metals, 70(13), 993996.More infoAbstract: In the framework of the quantum approach to electronelectron ("ee")• interactions in a magnetic field, two related phenomena, "magic angles" and "rapid magnetic oscillations", are investigated. We show that the sharp angular magnetoresistance dips have to exist at the main "magic angles" in Q1D metals due to the unusual dependence of "ee"  scattering on the direction of the magnetic field. We suggest that "rapid magnetic oscillations" are the result of the influence of a magnetic breakdown on "ee"scattering. Our calculations are in qualitative agreement with experimental data. © 1995.
 Lebed, A. G. (1995). New type of quantum magnetic resistance oscillations in quasionedimensional conductors. Physical Review Letters, 74(24), 49034906.More infoAbstract: We suggest an explanation for the "rapid magnetic oscillations" (RMO) in the metallic phase of the organic superconductor (TMTSF)2C1O4. It is based on the possibility of quantum magnetic oscillations in the probability of electronelectron scattering and thus exceeds the bounds of the standard description of the magnetic oscillations in metals. The calculated RMO frequency is in agreement with experimental data. The estimated temperature and magnetic field dependences of RMO magnitude are unusual.
 Gor'kov, L., & Lebed', A. (1993). Cyclotron resonance on open orbits in organic materials. Physical Review Letters, 71(23), 38743877.More infoAbstract: The cyclotron resonance on open orbits is suggested to demonstrate the one dimensional character of electron motion along the main conducting axis in the presence of a perpendicular magnetic field for organic materials with warped open Fermi surfaces. Singular behavior at resonant frequencies in the surface impedance and the helicon waves spectrum are obtained.
 Lebed, A. G. (1993). New type of magnetic resonance and giant quasionedimensional fluctuations in organic superconductors. Synthetic Metals, 57(2 3 pt 6), 46914696.More infoAbstract: We consider the fluctuation contribution to free energy of a quasionedimensional (Q1D) metal due to electronelectron (`ee') interaction in magnetic field. Electron paramagnetic momentum is found to become strongly temperature and pressure dependent in a broad temperature region, T≤200 K. Electron specific heat also has large fluctuation correction and exhibit nontrivial temperature behaviour. As a result of the influence of Zeemansplitting on processes of `ee'scattering, new angular oscillations of specific heat occur in magnetic field.
 Lebed, A. G. (1993). New type of magnetic resonance and giant quasionedimensional fluctuations in organic superconductors. Synthetic Metals, 57(23), 46914696.More infoAbstract: We consider the fluctuation contribution to free energy of a quasionedimensional (Q1D) metal due to electronelectron ("eee") interaction in magnetic field. Electron paramagnetic momentum is found to become strongly temperature and pressure dependent in a boad temperature region, T{lessthan or approximate} 200K. Electron specific heat also has large fluctuation correction and exhibit nontrivial temperature behaviour. As a result of the influence of Zeemansplitting on processes of "ee"scattering, new angular oscillations of specific heat occur in magnetic field. © 1993.
 Lebed, A. G. (1991). New phase transitions in the organic superconductor (TMTSF)_{2}ClO_{4}. Synthetic Metals, 42(12), 1938.More infoAbstract: The stability of spindensity wave formation in the organic superconductor (TMTSF)2ClO4 is studied. The anion gap in the electron spectrum causes reentrance of the metallic state in high magnetic fields. It also leads to fast oscillations of physical properties, in particular the phase transition temperature, versus magnetic field. Both these phenomena have been observed experimentally. © 1991.
 Lebed, A. G. (1991). New phases and quantum Hall effect in organic superconductors. Physica B: Condensed Matter, 169(1 4 pt 3), 368371.More infoAbstract: 'Umklapp processes' in quasionedimensional conductors (TMTSF)2X change their phase diagram qualitatively in the magnetic field. This leads to the coexistence of spindensity waves (SDW) characterized by different wave vectors. Earlier calculations on the quantum Hall effect in this situation appear to be incorrect and the Hall conductivity quantization follows from a more general theorem.
 Lebed, A. G. (1991). New phases and quantum Hall effect in organic superconductors. Physica B: Physics of Condensed Matter, 169(14), 368371.More infoAbstract: "Umklapp processes" in quasionedimensional conductors (TMTSF)2X change their phase diagram qualitatively in the magnetic field. This leads to the coexistence of spindensity waves (SDW) characterized by different wave vectors. Earlier calculations on the quantum Hall effect in this situation appear to be incorrect and the Hall conductivity quantization follows from a more general theorem. © 1991.
 Lebed, A. G., & Landau, L. D. (1991). New phase transitions in the organic superconductor (TMTSF)_{2}ClO_{4}. Synthetic Metals, 42(12), 1938.More infoAbstract: The stability of spindensity wave formation in the organic superconductor (TMTSF)2ClO4 is studied. The anion gap in the electron spectrum causes reentrance of the metallic state in high magnetic fields. It also leads to fast oscillations of physical properties, in particular the phase transition temperature, versus magnetic field. Both these phenomena have been observed experimentally.
 Lebed, A. G., & Bak, P. (1989). Theory of reentrance of spindensitywave transitions in bistetramethyltetraselenafulvalenium perchlorate [(TMTSF)2ClO4]. Physical Review B, 40(16), 1143311436.More infoAbstract: The stability of spindensitywave formation in the organic superconductor bistetramethyltetraselenafulvalenium perchlorate (TMTSF)2ClO4 is studied. The anion gap in the electron spectrum causes reentrance of the metallic state in high magnetic fields. It also leads to fast oscillations of physical properties, in particular, the phasetransition temperature versus magnetic field. Both these phenomena have been observed experimentally. © 1989 The American Physical Society.
 Lebed, A. G., & Bak, P. (1989). Theory of unusual anisotropy of magnetoresistance in organic superconductors. Physical Review Letters, 63(12), 13151317.More infoAbstract: We suggest that weak electron tunneling between layers is responsible for the experimentally observed dramatic deviations from twodimensional behavior in the magnetoresistance in the metallic phase of the quasitwodimensional conductors (TMTSF)2ClO4 and (TMTSF)2PF6. We predict a fine structure due to resonances in open orbits between motion parallel and perpendicular to the planes. © 1989 The American Physical Society.
 Burlachkov, L. I., Gor'kov, L., & Lebed', A. (1987). IDENTIFICATION OF THE SUPERCONDUCTIVITY TYPE IN ORGANIC SUPERCONDUCTORS.. Europhysics Letters, 4(8), 941946.More infoAbstract: Two phenomena are pointed out which, if observed, would testify that the superconductivity in the Bechgaard salts belongs to the triplet pairing: excitation of the spin waves in the radiofrequency fields and the superconductivity restoration in high enough magnetic fields H parallel b*.
 Burlachkov, L. I., Gor'kov, L., & Lebed', A. (1987). On the superconductivity type in the Bechgaard salts. Physica B+C, 148(13), 500502.More infoAbstract: The existence of the spin waves and the superconductivity restoration in high enough magnetic fields are predicted in case of the triplet pairing in the Bechgaard salts. © 1987.
 Gor'kov, L., & Lebed', A. (1984). ON THE STABILITY OF THE QUASIONEDIMENSIONAL METALLIC PHASE IN MAGNETIC FIELDS AGAINST THE SPIN DENSITY WAVE FORMATION.. Journal de physique. Lettres, 45(9), 433440.More infoAbstract: For a simple anisotropic metal model with two open nested Fermi surfaces, it is shown that the tendency to spin density wave formation increases when a magnetic field is applied, which could lead to a series of phase transitions as functions of the field value. The results are suggested as an explanation of the phase diagram of the (TMTSF)//2X compounds.
Presentations
 Lebed, A. G. (2021, April). Breakdown of the Equivalence Principle for a Quantum Body. April Meeting of American Physical Society. Online: APS.
 Lebed, A. G. (2021, July). Breakdown of the Equivalence Principle for a composite quantum body. 16th Marcel Grossmann meeting. Online.
 Lebed, A. G. (2021, July). Breakdown of the Equivalence Principle for a quantum body. Physical Interpretations of Relativity Theory  2021. Online.
 Lebed, A. G. (2021, March). Restoration of superconductivity in high magnetic fields in UTe2. March Meeting of Americal Physical Society. Online: APS.
 Lebed, A. G. (2020, Summer). Inequivalence between gravitational mass and energy for quantum body. RUSGRAV17 (International conference on gravitation, cosmology, and astrophysics). St. Petersburg, Russia.
 Lebed, A. G. (2019, July). Inequivalence between gravitation and inertial masses. Physical Interpretations of Relativity Theory  2019. Bauman Moscow State Technical University 5, 2nd Baumanskaya street, Moscow, 105005 Russia.
 Lebed, A. G. (2019, June). Some manybody phenomena due to quantum and quasiclassical effects of electron motion along open trajectories in a magnetic field. Modern Trends in Condensed Matter Physics (Lev Gor'kov Memorial Conference). Chernogolovka, Russia.
 Lebed, A. G. (2018, July). Inequivalence of active gravitational mass and energy due to quantum effects. !5th Marcel Grossmann International Conference. Rome, Italy.
 Lebed, A. G. (2018, October). Breakdown of the equivalence between gravitational mass and energy. Invited Colloqium at Boston College. Boston, MA, USA.
 Lebed, A. G. (2017, January). Inequivalence between Gravitational Mass and Energy for a Quantum Body. Testing Gravity 2017. Vancouver, Canada.
 Lebed, A. G. (2017, March). Inequality between Gravitational and Inertial Masses: Suggested Experiment on the Earth’s Orbit. 2017 IEEE Aerospace Conference. Big Sky, Montana, USA.
 Lebed, A. G. (2017, Spring). Inequality between Gravitational and Inertial Masses. Cooquium at Physis Department of UofA. Tucson, AZ, USA.
 Lebed, A. G. (2016, July). Inequivalence between active gravitational mass and energy for a quantum body. 21st International Conference on General Relativity and Gravitation. New York City.
 Lebed, A. G. (2016, March). Possible existence of superconductivity in ultrahigh magnetic fields. American Physical Society March Meeting. Baltimore.
 Lebed, A. G. (2015, August). Possible triplet superconductivity and its main features in the quasionedimensional conductor Li(0.9)Mo(6)O(17). Materials and Mechanisms of Superconductivity (M2S2015). Geneva, Switzerland: National Science Foundation.
 Lebed, A. G. (2015, March/Spring). Possible restoration of superconductivity in the quasionedimensional conductor Li$_{0.9}$Mo$_6$O$_{17}$ in pulsed high magnetic field $H\approx 100$ T. March Meeting of the American Physical Society. San Antonio, Texas, USA: National Science Foundation.
 Lebed, A. G. (2014, April). Breakdown of the Equivalence between Gravitational Mass and Energy. April Meeting of the American Physical Society. Savannah, GA, USA.
 Lebed, A. G. (2014, August). Quantum Limit for Triplet Superconductivity in a QuasiOneDimensional Conductor. ISCOM2014. Cargese, Corsica, France.
 Lebed, A. G. (2014, March). Possible Restoration of Triplet Superconductivity in High Magnetic Fields. March Meeting of the American Physical Society. Denver, CO, USA.