Nonequilibrium Josephson effect in mesoscopic ballistic multiterminal SNS junctions

TL;DR

This paper investigates how nonequilibrium conditions affect Josephson currents and conductance in ballistic multiterminal SNS junctions, revealing voltage-dependent current suppression, phase oscillations, and resonant behaviors influenced by interface barriers.

Contribution

It provides a comprehensive analysis of nonequilibrium effects in multiterminal SNS junctions, including phase-dependent conductance oscillations and resonance phenomena due to barriers, which are novel insights.

Findings

Josephson current can be suppressed or reversed by quasiparticle injection.

Conductance shows a finite bias anomaly around specific voltages.

Resonant behavior of Josephson current depends on junction length and barriers.

Abstract

We present a detailed study of nonequilibrium Josephson currents and conductance in ballistic multiterminal SNS-devices. Nonequilibrium is created by means of quasiparticle injection from a normal reservoir connected to the normal part of the junction. By applying a voltage at the normal reservoir the Josephson current can be suppressed or the direction of the current can be reversed. For a junction longer than the thermal length, $L\gg\xi_T$, the nonequilibrium current increases linearly with applied voltage, saturating at a value equal to the equilibrium current of a short junction. The conductance exhibits a finite bias anomaly around $eV \sim \hbar v_F/L$. For symmetric injection, the conductance oscillates $2\pi$-periodically with the phase difference $\phi$ between the superconductors, with position of the minimum ($\phi=0$ or $\pi$) dependent on applied voltage and temperature. For asymmetric injection, both the nonequilibrium Josephson current and the conductance becomes $\pi$-periodic in phase difference. Inclusion of barriers at the NS-interfaces gives rise to a resonant behavior of the total Josephson current with respect to junction length with a period $\sim \lambda_F$. Both three and four terminal junctions are studied.