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V. P. Mineev

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

At least 55 records · Page 3Linked to original sources
arXiv2013

Magnetic relaxation in uranium ferromagnetic superconductors

There is proposed a phenomenological theory of quasi-elastic neutron scattering in the itinerant ferromagnets UGe$_2$ and UCoGe based on their property that magnetization supported by the moments located at uranium atoms is not conserved quantity relaxing to equilibrium by the interaction with itinerant electrons subsystem. As result the line width of quasi elastic neutron scattering at $q\to 0$ acquires nonvanishing value at all temperatures but the Curie temperature.

cond-mat.str-el↗
arXiv2013

Half - Quantum Vortices

Unlike to superfluid $^4$He the superfluid $^3$He-A support the existence of vortices with half quantum of circulation as well as single quantum vortices. The singular single quanta vortices as well as nonsingular vortices with 2 quanta of circulation have been revealed in rotating $^3$He-A. However, the half quantum vortices in open geometry always possess an extra energy due to spin-orbit coupling leading to formation of domain wall at distances larger than dipole length $\sim 10^{-3}cm$ from the vortex axis. Fortunately the same magnetic dipole-dipole interaction does not prevent the existence of half-quantum vortices in the polar phase of superfluid $^3$He recently discovered in peculiar porous media "nematically ordered" aerogel. Here we discuss this exotic possibility. The discoveries of half-quantum vortices in triplet pairing superconductor Sr$_2$RuO$_4$ as well in the exciton-polariton condensates are the other parts of the story about half-quantum vortices also described in the paper.

cond-mat.supr-con↗
arXiv2012

Whether there is the intrinsic Hall effect in a multi-band superconductor?

The interplay of the microscopic models and the symmetry considerations in application to the superconducting state of putative chiral superconductor Sr2RuO4 are presented. There is demonstrated that chiral two-band superconducting ordering recently proposed as candidate for the superconducting state in this material and having the long-expected property such as the intrinsic Hall effect does not exist as energetically disadvantageous in comparison with the states not supporting the Hall effect. Other chiral multi-band superconducting states with intraband pairing do not support an intrinsic Hall properties as well. The superconducting states with direct interband pairing could serve as the probable candidates for the Hall effect existence.

cond-mat.supr-con↗
arXiv2012

Temperature-dependent Ginzburg-Landau parameter

Taking into account both the orbital and the paramagnetic depairing effects we derive a simple analytic formula for the temperature dependence of the Ginzburg-Landau parameter valid in vicinity of field dependent critical temperature in a type-II superconductor.

cond-mat.supr-con↗
arXiv2012

Fermi liquid theory and ferromagnetism

There is demonstrated that an isotropic ferromagnetic Fermi liquid reveals instability of the ferromagnetic state in respect to the transversal inhomogeneous deviations of magnetization from equilibrium. The result was obtained by derivation of the spin waves spectrum by means of kinetic equation.

cond-mat.quant-gas↗
arXiv2011

Phase diagram of UGe2. Whether there are quantum phase transitions ?

The phase diagram of several itinerant ferromagnets reveals the common feature. The phase transition temperature decreases with pressure increase and reaches zero value at some critical pressure $P_c$ such that at low enough temperatures one can expect critical behavior specific for quantum phase transition. It is not the case, however. Being the second order at ambient pressure the transition from paramagnetic to ferromagnetic state at high pressures - low temperatures is transformed to the discontinuous jump. We discuss the magneto-elastic mechanism of development of the first order type instability at the phase transition to the ferromagnet state in strongly anisotropic ferromagnet UGe2. Using the parameters characterizing the properties of UGe$_2$ we argue the effectiveness of this mechanism transforming the very weak first order type transition to the really observable one.

cond-mat.str-el↗
arXiv2011

Field-Induced Spin-Exciton Condensation in dx2-y2-wave Superconducting CeCoIn5

The implications of the spin exciton mechanism are exposed in the context of a Spin Density Wave (SDW) instability occurring inside the superconducting phase of a layered heavy electron compound. In this model a magnetic field serves as a tuning parameter bringing the system to the point where the transverse spin correlations are enhanced due to dx2 -y2 -wave superconductivity and induces an instability to a phase with coexisting superconductivity and SDW order. The model considers electrons in a crystal with antiferromagnetic interactions and provides restrictions on the Fermi surface characteristics and on the ordering wave-vector (that can be commensurate or incommensurate close to commensuration). The applications of the model are addressed to the low-temperature/high-magnetic-field phase of CeCoIn5 [M. Kenzelmann et al., Science 321, 1652 (2008), Phys. Rev. Lett. 104, 127001 (2010)].

cond-mat.supr-con↗
arXiv2011

On the phase diagram of UGe2

The magneto-elastic mechanism of development of the first order type instability at the phase transition to the ferromagnet state in itinerant ferromagnet-superconductor UGe2 is discussed. The particular property of this material is the precipitous drop of the critical temperature at pressure increase near 14-15 kbar that drastically increases the temperature of the first order instability in respect to the critical temperature. This effect leading to transformation of the second order type transition to the first order one is determined also by the specific heat increase in the temperature interval of the development of critical fluctuations. After performing the necessary calculations and estimations using the parameters characterizing the properties of UGe2 we argue the effectiveness of this mechanism.

cond-mat.str-el↗
arXiv2010

Magnetic field dependence of pairing interaction in ferromagnetic superconductors with triplet pairing

It is developed a microscopic description of superconductivity in ferromagnetic materials with triplet pairing triggered by the exchange of magnetic fluctuations. Instead widely used paramagnon model we work with phenomenological spectrum of fluctuations in the orthorhombic ferromagnet with strong magnetic anisotropy. Depending of the field orientation parallel or perpendicular to the direction of spontaneous magnetization the effective amplitude of pairing interaction proves to be decreasing or increasing function of magnetic field that allows to explain the drastic difference in magnitudes of upper critical field in these directions.

cond-mat.supr-con↗
arXiv2010

Polarization Effects in Superfluid $^4$He

A theory of thermoelectric phenomena in superfluid $^4He$ is developed. It is found an estimation of the dipole moment of helium atom arising due to electron shell deformation caused by pushing forces from the side of its surrounding atoms. The corresponding electric signal generated in a liquid consisting of electrically neutral atoms by the ordinary sound waves is found extremely small. The second sound waves in superfluid $^4He$ generate the polarization of liquid induced by the relative accelerated motion of the superfluid and the normal component. The derived ratio of the amplitudes of temperature and electric polarization potential was proved to be practically temperature independent. Its magnitude is in reasonable correspondence with the experimental observations. The polarity of electric signal is determined by the sign of temperature gradient in accordance with the measurements. The problem of the roton excitations dipole moment is also discussed.

cond-mat.other↗
arXiv2010

Paramagnetic Effects in the Vortex Lattice Field Distribution of Strongly Type-II Superconductors

We present an analysis of the magnetic field distribution in the Abrikosov lattice of high-$κ$ superconductors with singlet pairing in the case where the critical field is mainly determined by the Pauli limit and the superfluid currents partly come from the paramagnetic interaction of electron spins with the local magnetic field. The derivation is performed in the frame of the generalized Clem variational method which is valid not too close to the critical field and furthermore with the Abrikosov type theory in the vicinity of it. The found vortex lattice form factor increases with increasing field and then falls down at approach of the upper critical field where the superconducting state is suppressed.

cond-mat.supr-con↗
arXiv2010

Paramagnetic limiting in ferromagnetic superconductors with triplet pairing

The spin susceptibility in the uranium ferromagnet superconductors is calculated. There is shown that the absence of superconductivity paramagnetic limitation for the field directions perpendicular to the direction of the spontaneous magnetization is explained by the itinerant ferromagnet band splitting rather than by a rotation of magnetization toward the external field direction. The qualitative description of the upper critical field temperature dependence is given.

cond-mat.supr-con↗
arXiv2010

Paramagnetic Effects on the Vortex Lattice of the Unconventional Superconductor CeCoIn_5

We expose an analysis of the magnetic field distribution in the Abrikosov lattice of high-kappa superconductors with d-wave pairing in the case where the critical field is mainly determined by the Pauli limit and the superfluid currents mainly come from the paramagnetic interaction of electron spins with the local magnetic field. The result found in frame of the generalized Clem variational approach is compatible with the recent observation that the form factor in CeCoIn_5 increases with increasing field and then decreases at the approach of H_c2. (A. D. Bianchi et al., Science vol. 319, 177 (2008)).

cond-mat.supr-con↗
arXiv2009

Roton dipole moment

The roton excitation in the superfluid He-4 does not possess a stationary dipole moment. However, a roton has an instantaneous dipole moment, such that at any given moment one can find it in the state either with positive or with negative dipole moment projection on its momentum direction. The instantaneous value of electric dipole moment of roton excitation is evaluated. The result is in reasonable agreement with recent experimental observation of the splitting of microwave resonance absorption line at roton frequency under external electric field.

cond-mat.other↗
arXiv2009

Recent developments in unconventional superconductivity theory

The review of recent developments in the unconventional superconductivity theory is given. In the fist part I consider the physical origin of the Kerr rotation polarization of light reflected from the surface of superconducting $Sr_2RuO_4$. Then the comparison of magneto-optical responses in superconductors with orbital and spin spontaneous magnetization is presented. The latter result is applied to the estimation of the magneto-optical properties of neutral superfluids with spontaneous magnetization. The second part is devoted to the natural optical activity or gyrotropy properties of noncentrosymmetric metals in their normal and superconducting states. The temperature behavior of the gyrotropy coefficient is compared with the temperature behavior of paramagnetic susceptibility determining the noticeable increase of the paramagnetic limiting field in noncentrosymmetric superconductors. In the last chapter I describe the order parameter and the symmetry of superconducting state in the itinerant ferromagnet with orthorhombic symmetry. Finally the Josephson coupling between two adjacent ferromagnet superconducting domains is discussed.

cond-mat.supr-con↗
arXiv2009

Introduction to superconductivity in metals without inversion center

This Chapter gives a brief introduction to some basic aspects metals and superconductors in crystal without inversion symmetry. In a first part we analyze some normal state properties which arise through antisymmetric spin-orbit coupling existing in non-centrosymmetric materials and show its influence on the de Haas-van Alphen effect. For the superconducting phase we introduce a multi-band formulation which naturally arises due the spin splitting of the bands by spin-orbit coupling. It will then be shown how the states can be symmetry classified and their relation to the original classification in even-parity spin-singlet and odd-parity spin-triplet pairing states. The general Ginzburg-Landau functional will be derived and applied to the nucleation of superconductivity in a magnetic field. It will be shown that magneto-electric effects can modify the standard paramagnetic limiting behavior drastically.

cond-mat.supr-con↗
arXiv2009

Coexistence of triplet superconductivity and itinerant ferromagnetism

The triplet superconductivity in $UGe_2$ and $URhGe$ coexists with itinerant ferromagnetism such that in the pressure-temperature phase diagram the whole region occupied by the superconducting state is situated inside a more vast ferromagnetic region. In the same family metal UCoGe the pressure dependent critical lines T_{Curie}(P) and T_{sc}(P) of the ferromagnet and the superconducting phase transitions intersect each other. The two-band multidomain superconducting ferromagnet state arises at temperatures below both of these lines. Here I describe the symmetry and the order parameters of the paramagnet as well of the multidomain ferromagnet superconducting states. The Josephson coupling between two adjacent ferromagnet superconducting domains is discussed.

cond-mat.supr-con↗