arXiv subjects

B. N. Narozhny

Publications and source records attributed to B. N. Narozhny.

40 records · Page 3Linked to original sources

arXiv1999

Phase Fluctuations and Non-Equilibrium Josephson Effect

We consider a diffusive S-N-S junction with electrons in the normal layer driven out of equilibrium by external bias. We show that, the non-equilibrium fluctuations of the electron density in the normal layer cause the fluctuations of the phase of the order parameter in the S-layers. As a result, the magnitude of the Josephson current in the non-equilibrium junction is significantly supressed relative to its mean field value.

cond-mat.supr-con↗

arXiv1999

Theory of Interaction Effects in N-S Junctions out of Equilibrium

We consider a normal metal - superconductor (N-S) junction in the regime, when electrons in the normal metal are driven out of equilibrium. We show that the non-equilibrium fluctuations of the electron density in the N-layer cause the fluctuations of the phase of the order parameter in the S-layer. As a result, the density of states in the superconductor deviates from the BCS form, most notably the density of states in the gap becomes finite. This effect can be viewed as a result of the time reversal symmetry breaking due to the non-equilibrium, and can be described in terms of a low energy collective mode of the junction, which couples normal currents in N-layer and supercurrents. This mode is analogous to the Schmid-Schön mode. To interpret their measurements of the tunneling current, Pothier {\em et. al} [Phys. Rev. Lett. {\bf 79}, 3490 (1997)] had to assume that the energy relaxation rate in the normal metal is surprisingly high. The broadening of the BCS singularity of the density of states in the S-layer manifest itself similarly to the broadening of the distribution function. Mechanism suggested here can be a possible explanation of this experimental puzzle. We also propose an independent experiment to test our explanation.

cond-mat.mes-hall↗

arXiv1998

Resistance of Josephson Junction Arrays at Low Temperatures

We study motion of vortices in arrays of Josephson junctions at zero temperature where it is controlled by quantum tunneling from one plaquette to another. The tunneling process is characterized by a finite time and can be slow compared to the superconducting gap (so that $τΔ>> 1$). The dissipation which accompanies this process arises from rare processes when a vortex excites a quasiparticle above the gap while tunneling through a single junction. We find that the dissipation is significant even in the case $τΔ>> 1$, in particular it is not exponentially small in this parameter. We use the calculated energy dissipation for the single vortex jump to estimate the physical resistance of the whole array.

cond-mat.soft↗

arXiv1998

Low temperature transport in the XXZ model

We present evidence suggesting that spin transport in the gapless phase of the S=1/2 XXZ model is ballistic rather than diffusive. We map the model onto a spinless fermion model whose charge stiffness determines the spin transport of the original model. By means of exact numerical diagonalisation and finite size scaling we study both the stiffness and the level statistics. We show that the stiffness is non-zero at low temperatures so that the transport is ballistic. Our results suggest that the non-zero stiffness is due to the fact that even in the presence of Umklapp scattering a non-zero fraction of states remain degenerate in the thermodynamic limit.

cond-mat↗