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V. P. Mineev

Publications and source records attributed to V. P. Mineev.

At least 73 records · Page 4Linked to original sources
arXiv2009

Natural optical activity of metals

We derive the current response of noncentrosymmetric metal in normal and in superconducting states to the electromagnetic field with finite frequency and wave vector. The conductivity tensor is found contains the linear in wave vector off diagonal part generating natural optical activity. The Kerr rotation of polarization of light reflected from the metal surface is calculated. Its value is expressed through the fine-structure constant and the ratio of light frequency to the band splitting due to the spin-orbit interaction.

cond-mat.str-el↗
arXiv2008

Nonuniform states in noncentrosymmetric superconductors

In noncentrosymmetric crystals, nonuniform superconducting states are possible even in the absence of any external magnetic field. The origin of these states can be traced to the Lifshitz invariants in the free energy, which are linear in spatial gradients. We show how various types of the Lifshitz invariants in noncentrosymmetric superconductors can be derived from microscopic theory.

cond-mat.supr-con↗
arXiv2008

Pressure-temperature phase diagram of ferromagnetic superconductors

The symmetry approach to the description of the (P,T) phase diagram of ferromagnet superconductors with triplet pairing is developed. Taking into account the recent experimental observations made on UCoGe it is considered the case of a crystal with orthorhombic structure and strong spin-orbital coupling. It is shown that formation of ferromagnet superconducting state from a superconducting state is inevitably accompanied by the first order type transition.

cond-mat.supr-con↗
arXiv2008

Gap structure in noncentrosymmetric superconductors

Gap structure in noncentrosymmetric superconductors with spin-orbit band splitting is studied using a microscopic model of pairing mediated by phonons and/or spin fluctuations. The general form of pairing interaction in the band representation is derived, which includes both the intraband and interband pairing terms. In the case of isotropic interaction (in particular, for a BCS-contact interaction), the interband pairing terms vanish identically at any magnitude of the band splitting. The effects of pairing interaction anisotropy are analyzed in detail for a metal of cubic symmetry with strong spin-orbit coupling. It is shown that if phonons are dominant then the gaps in two bands are isotropic, nodeless, and have in general different amplitudes. Applications to the Li_2(Pd_{1-x},Pt_x)_3B family of noncentrosymmetric superconductors are discussed.

cond-mat.supr-con↗
arXiv2008

Electromagnetic response of unconventional superconductors

We derive the current response to the linearly polarized electromagnetic field with finite frequency and wave vector incident normally on the specular surface of a clean nonconventional superconductor with orbital spontaneous magnetization parallel to the crystal axis and perpendicular to the crystal surface. The result includes the usual part known from the theory of conventional superconductivity and as well the magneto-optical term typical for the superconductors with spontaneous time reversal breaking. As an application of the basic current-field relation we consider the Kerr effect for the rotation of polarization of infrared light reflected from the superconductor surface.

cond-mat.supr-con↗
arXiv2007

In-plane magnetic field phase diagram of superconducting Sr2RuO4

We develop the Ginzburg - Landau theory of the upper critical field in the basal plane of a tetragonal multiband metal in two-component superconducting state. It is shown that typical for the two component superconducting state the upper critical field basal plane anisotropy and the phase transition splitting still exist in a multiband case. However, the value of anisotropy can be effectively smaller than in the single band case. The results are discussed in the application to the superconducting Sr2RuO4.

cond-mat.supr-con↗
arXiv2007

Sr_2 Ru O_4 : Broken Time-Reversal Symmetry in the Superconducting state

Using a phenomenological two-fluid model we derive the Kerr rotation of the polarization direction of reflected light from the surface of a superconductor in a state breaking time-reversal symmetry. We argue that this effect found recently in the superconducting state of $Sr_2RuO_4$ by Xia et al (Phys.Rev.Lett. {\bf 97}, 167002 (2006)) originates from the spontaneous magnetization in this superconductor. The temperature and the frequency dependencies of the effect are established. It is shown that the effect is determined by one of two mechanisms depending on the frequency of light that is larger or smaller than the plasma frequency. The mechanism originating from the gradient of chemical potential created by the electric field of light penetrating into the skin layer and important at frequencies larger than the plasma frequency was missed in the preliminary version of this paper (V.P.Mineev, arXiv:cond-mat/0703624v2).

cond-mat.supr-con↗
arXiv2007

Effects of impurities on superconductivity in noncentrosymmetric compounds

We microscopically derive the Ginzburg-Landau free energy functional for a noncentrosymmetric superconductor with a large spin-orbit splitting of the electron bands, in the presence of nonmagnetic impurities. The critical temperature is found to be suppressed by disorder, both for conventional and unconventional pairing, in the latter case according to the universal Abrikosov-Gor'kov function. The impurity effect on the upper critical field turns out to be nonuniversal, determined by the pairing symmetry and the band structure. In a BCS-like model, Tc is not affected, while Hc2 increases with disorder. For unconventional pairing, both Tc and Hc2 are suppressed by disorder.

cond-mat.supr-con↗
arXiv2007

Electrodynamics of Fulde-Ferrell-Larkin-Ovchinnikov superconducting state

We develop the Ginzburg-Landau theory of the vortex lattice in clean isotropic three-dimensional superconductors at large Maki parameter, when inhomogeneous Fulde-Ferrell-Larkin-Ovchinnikov state is favored. We show that diamagnetic superfluid currents mainly come from paramagnetic interaction of electron spins with local magnetic field, and not from kinetic energy response to the external field as usual. We find that the stable vortex lattice keeps its triangular structure as in usual Abrikosov mixed state, while the internal magnetic field acquires components perpendicular to applied magnetic field. Experimental possibilities related to this prediction are discussed.

cond-mat.supr-con↗
arXiv2006

Comment on "Magnetic quantum oscillations of the conductivity in layered conductors"

We discuss the recent theory of Gvozdikov [Phys. Rev. B 70, 085113 (2004)] which aims at explaining the Shubnikov-de Haas oscillations of the longitudinal resistivity ρ_zz observed in the quasi-two-dimensional organic compound β''-(BEDT-TTF)_2SF_5CH_2CF_2SO_3. We point out that the self-consistent equations of the theory yielding the longitudinal resistivity and the magnetic field dependence of the chemical potential have been incorrectly solved. We show that the consideration of the self-consistent Born approximation (which determines the relaxation rate in Gvozdikov's paper) leads in fact to the complete absence of the longitudinal conductivity σ_{zz} at leading order in high magnetic fields.

cond-mat.other↗
arXiv2006

Interplay of paramagnetic, orbital and impurity effects on the phase transition of a normal metal to superconducting state

We derive the generalized Ginzburg-Landau free energy functional for conventional and unconventional singlet superconductors in the presence of paramagnetic, orbital and impurity effects. Within the mean field theory, we determine the criterion for appearence of the non uniform (Fulde-Ferrell-Larkin-Ovchinnikov) superconducting state, with vortex lattice structure and additional modulation along the magnetic field. We also discuss the possible change of the order of transition from normal to superconducting state. We find that the superconducting phase diagram is very sensitive to geometrical effects such as the nature of the order parameter and the shape of the Fermi surface. In particular, we obtain the qualitative phase diagrams for three-dimensional isotropic s-wave superconductors and in quasi two-dimensional d-wave superconductors under magnetic field perpendicular to the conducting layers. In addition, we determine the criterion for instability toward non uniform superconducting state in s-wave superconductors in the dirty limit.

cond-mat.supr-con↗
arXiv2005

Transverse spin waves in isotropic ferromagnets

The comparison of transverse spin wave spectra and its attenuation in Heisenberg ferromagnet and in ferromagnetic Fermi liquid as well in polarized Fermi liquid is undertaken. The transverse spin waves frequency in polarized paramagnetic Fermi liquid as well in a Fermi liquid with spontaneous magnetization is found to be proportional to the square of the wave vector with complex diffusion coefficient such that the damping has a finite value proportional to the scattering rate of quasiparticles at T=0. This behavior of polarized Fermi liquid contrasts with the behavior of Heisenberg ferromagnet in hydrodynamic regime where the transverse spin wave attenuation appears in terms proportional to the wave vector in fourth power. The reactive part of diffusion coefficient in paramagnetic state at T=0 proves to be inversely proportional to magnetization whereas in ferromagnetic state it is directly proportional to magnetization. The dissipative part of diffusion coefficient at T=0 in paramagnetic state is polarization independent, whereas in ferromagnetic state it is proportional to square of magnetization. Moreover, the spin wave spectrum in ferromagnetic Fermi liquid proves to be unstable that demonstrates the difficulty of the Fermi liquid description of itinerant ferromagnetism.

cond-mat.str-el↗
arXiv2005

Theory of transverse spin dynamics in a polarized Fermi liquid and an itinerant ferromagnet

The linear equations for transverse spin dynamics in a weakly polarized degenerate Fermi liquid with arbitrary relationship between temperature and polarization are derived from Landau-Silin phenomenological kinetic equation with general form of two-particle collision integral. Unlike the previous treatment where Fermi velocity and density of states have been taken as constants independent of polarization here we made derivation free from this assumption. The obtained equations are applicable for description of spin dynamics in paramagnetic Fermi liquid with finite polarization as well in an itinerant ferromagnet. In both cases transverse spin wave frequency is found to be proportional to the square of the wave vector with complex constant of proportionality (diffusion coefficient) such that the damping has a finite value at T=0. The polarization dependence of the diffusion coefficient is found to be different for a polarized Fermi liquid and for an itinerant ferromagnet. These conclusions are confirmed by derivation of transverse spin wave dispersion law in frame of field theoretical methods from the integral equation for the vortex function. It is shown that similar derivation taking into consideration the divergency of static transverse susceptibility also leads to the same attenuating spin wave spectrum.

cond-mat.str-el↗
arXiv2005

Interplay between magnetism and superconductivity in URhGe

The magnetization rotation transition occurs in the itinerant ferromagnet URhGe when the field about 12T is applied in direction perpendicular to spontaneous magnetization in the plane of the smallest magnetic anisotropy energy.The transition is accompanied by the maximum of resistivity in the normal state and by reentrance of superconductivity at lower temperatures in the field interval between 8 and 13 Tesla [F.Levy et al, Science, to be published (2005)]. We discuss the magnetization orientation transition and the modification of triplet pairing superconducting state coexisting with ferromagnetism up to the fields about 2 Tesla and then reappearing in the broad vicinity of the transition. The nonsymmorphic space group crystal symmetry of ferromagnetic URhGe allows existance of antiferromagnetic ordering of magnetic moments of pairs of uranium atoms along a-axis. We show that the amplitude of this weak antiferromagnetic ordering increases below the phase transition into superconducting state due to Cooper pairs spontaneous magnetism.

cond-mat.supr-con↗
arXiv2005

Interplay between SDW and induced local moments in URu2Si2

Theoretical model for magnetic ordering in the heavy-fermion metal URu2Si2 is suggested. The 17.5K transition in this material is ascribed to formation of a spin-density wave, which develops due to a partial nesting between electron and hole parts of the Fermi surface and has a negligibly small form-factor. Staggered field in the SDW state induces tiny antiferromagnetic order in the subsystem of localized singlet-singlet levels. Unlike the other models our scenario is based on coexistence of two orderings with the same antiferromagnetic dipole symmetry.The topology of the pressure phase diagram for such a two order parameter model is studied in the framework of the Landau theory. The field dependences of the staggered magnetization and the magnon gap are derived from the microscopic theory and found to be in good quantitative agreement with experiment.

cond-mat.str-el↗