arXiv subjects

Alex Levchenko

Publications and source records attributed to Alex Levchenko.

131 records · Page 8Linked to original sources

arXiv2007

Coulomb drag at zero temperature

We show that the Coulomb drag effect exhibits saturation at small temperatures, when calculated to the third order in the interlayer interactions. The zero-temperature transresistance is inversely proportional to the third power of the dimensionless sheet conductance. The effect is therefore the strongest in low mobility samples. This behavior should be contrasted with the conventional (second order) prediction that the transresistance scales as a certain power of temperature and is almost mobility-independent. The result demonstrates that the zero-temperature drag is not an unambiguous signature of a strongly-coupled state in double-layer systems.

cond-mat.mes-hall↗

arXiv2007

Singular length dependence of critical current in SNS bridges

We examine dependence of the critical Josephson current on the length L of the normal bridge N between two bulk superconductors. This dependence turns out to be nonanalytic at small L. The nonanalyticity originates from the contribution of extended quasiparticle states with energies well above the superconducting gap. This should be contrasted with the more familiar contribution to the Josephson current coming from Andreev bound states localized in the normal region at energies below the gap.

cond-mat.supr-con↗

arXiv2007

Keldysh Ginzburg-Landau action of fluctuating superconductors

We derive Ginzburg-Landau action by systematically integrating out electronic degrees of freedom in the framework of the Keldysh nonlinear sigma-model of disordered superconductors. The resulting Ginzburg-Landau functional contains a nonlocal $Δ$-dependent contribution to the diffusion constant, which leads, for example, to Maki-Thompson corrections. It also exhibits an anomalous Gor'kov-Eliashberg coupling between $Δ$ and the scalar potential, as well as a peculiar nonlocal nonlinear term. The action is gauge invariant and satisfies the fluctuation dissipation theorem. It may be employed e.g. for calculation of higher moments of the current fluctuations.

cond-mat.supr-con↗

arXiv2004

Magnetization suppression of Type-II Superconductors by external alternating magnetic field

The effect of suppression of static magnetization of an anisotropic hard superconductor by alternating magnetic field is analyzed theoretically. The magnetic moment suppression dynamics is described with respect to the magnetization loop of the superconductor. It is found that in some cases the magnetic moment varies nonmonotonically with the growth in amplitude $\mathrm{h}$ of the alternating field. Effect of transition, induced by $\mathrm{\mathbf{h}}(t)$, of superconductor form paramagnetic into the diamagnetic state is considered. The amplitude of alternating magnetic field $\mathrm{h}_{c}(δ,\vartheta)$ for which the complete suppression of the magnetization occurs is calculated as the function of anisotropy parameter $δ$ and it orientation angle $\vartheta$ with respect to the crystallographic axes of the sample.

cond-mat.supr-con↗

arXiv2004

Inelastic quantum tunneling through disordered potential barrier

The effect of inelastic scattering on quantum tunneling through a rectangular potential barrier, of length $L$, containing randomly distributed impurities, is considered. It is shown that, despite the fact that the inelastic transition probability $\mathcal{T}_{\mathrm{inelastic}}$ is exponentially small, it may be greater than that of the elastic in the out of resonance conditions for some energy interval $\triangle E$ (the energy of the incident particle is far from the spectrum of the random Hamiltonian). The asymptotic of the tunnelling transition probability for various impurity configurations are found and the energy interval $\triangle E$ where $\mathcal{T}_{\mathrm{elastic}}\sim\exp(-L/L^{*})\lesssim\mathcal{T}_{\mathrm{i nelastic}}$ is determined.

cond-mat.dis-nn↗