arXiv subjects

V. Braude

Publications and source records attributed to V. Braude.

9 recordsLinked to original sources

arXiv2007

Triplet Josephson effect with magnetic feedback

We study AC Josephson effect in a superconductor-ferromagnet heterostructure with a variable magnetic configuration. The system supports triplet proximity correlations whose dynamics is coupled to the magnetic dynamics. This feedback dramatically modifies the behavior of the junction. The current-phase relation becomes double-periodic at both very low and high Josephson frequencies $ω_J$. At intermediate frequencies, the periodicity in $ω_J t$ may be lost.

cond-mat.supr-con↗

arXiv2006

Microwave Response and Spin Waves in Superconducting Ferromagnets

Excitation of spin waves is considered in a superconducting ferromagnetic slab with the equilibrium magnetization both perpendicular and parallel to the surface. The surface impedance is calculated and its behavior near propagation thresholds is analyzed. Influence of non-zero magnetic induction at the surface is considered in various cases. The results provide a basis for investigation of materials with coexisting superconductivity and magnetism by microwave response measurements.

cond-mat.supr-con↗

arXiv2006

Orbital magnetic dynamics in chiral p-wave superconductors

We present a theory of orbital magnetic dynamics for a chiral p-wave superconductor with broken time-reversal symmetry. In contrast to the common Landau-Lifshitz theory for spin ferromagnets, the case of orbital magnetism cannot be described in terms of local magnetization density. Hence it is impossible to define unambiguously the spontaneous magnetic moment: the latter would depend on conditions of its experimental investigation. As an example of this we consider orbital magnetization waves and the domain structure energy.

cond-mat.supr-con↗

arXiv2006

Fully developed triplet proximity effect

We present a model for fully developed triplet proximity effect in superconductor-ferromagnet heterostructures. Within the circuit-theory approximation, we evaluate the Green's functions, the density of states, and the Josephson current that depend essentially on the magnetization configuration.

cond-mat.supr-con↗

arXiv2005

Surface spin waves in superconducting and insulating ferromagnets

Surface magnetization waves are studied on a semi-infinite magnetic medium in the perpendicular geometry. Both superconducting and insulating ferromagnets are considered. Exchange and dipole energies are taken into account, as well as retardation effects. At large wave vectors, the spectrum for a superconductor and insulator is the same, though for the former the branch is terminated much earlier than for the latter due to excitation of plasmons. At small wave vectors, the surface wave is more robust in the superconductor since it is separated from the bulk continuum by a finite gap.

cond-mat.str-el↗

arXiv2003

Excitation of Spin Waves in Superconducting Ferromagnets

This Letter presents a theoretical analysis of propagation of spin waves in a superconducting ferromagnet. The surface impedance was calculated for the case when the magnetization is normal to the sample surface. We found the frequencies at which the impedance and the power absorption have singularities related to the spin wave propagation, and determined the form of these singularities. With a suitable choice of parameters, there is a frequency interval in which two propagating spin waves of the same circular polarization are generated, one of them having a negative group velocity.

cond-mat↗

arXiv2002

Vortex shear effects in layered superconductors

Motivated by recent transport and magnetization measurements in BSCCO samples [B. Khaykovich et. al., Phys. Rev. B 61, R9261 (2000)], we present a simple macroscopic model describing effects of inhomogeneous current distribution and shear in a layered superconductor. Parameters of the model are deduced from a microscopic calculation. Our model accounts for the strong current non-linearities and the re-entrant temperature dependence observed in the experiment.

cond-mat.supr-con↗

arXiv2002

Frictional drag in dilute bilayer 2D hole systems

We develop a theory for frictional drag between two 2D hole layers in a dilute bilayer GaAs hole system, including effects of hole-hole and hole-phonon interactions. Our calculations suggest significant enhancement of hole drag transresistivity over the corresponding electron drag results. This enhancement originates from the exchange induced renormalization of the single layer compressibility and the strong dependence of single layer conductivity on density. We also address the effect of hole-phonon interaction on the drag temperature dependence. Our calculated results are in reasonable quantitative agreement with recent experimental observations.

cond-mat.str-el↗

arXiv2001

Coulomb drag between a metal and a Wigner crystal

We calculated the Coulomb drag contribution to the resistivity and the transresistivity for a double layer system, in which the passive layer is a Wigner crystal pinned by impurities, and the active one is a metal. We found that in quasi one dimensional systems both quantities are suppressed at low temperatures by the constraints of energy and momentum conservation in electron-phonon scattering. In two dimensions both quantities are ~T^4, which is consistent with Bloch law for the contribution of electron-phonon interaction to the resistivity. Strong impurities in the Wigner crystal decrease the transresistivity significantly when their number reaches the logarithm of the number of sites in the crystal. In contrast, the drag contribution to the resistivity is found to be independent of the impurities, at least as long as their density is kept zero in the thermodynamic limit.

cond-mat↗