Anomalous supercurrents in the presence of particle losses

TL;DR

This paper investigates how single-particle losses affect supercurrent behavior in superfluid or superconducting junctions, revealing anomalous current reversal and enhancement effects due to dissipation.

Contribution

It introduces a theoretical framework showing dissipation-induced modifications to Josephson currents, including current reversal and enhancement regimes, using Keldysh field theory and Lindblad master equations.

Findings

Supercurrent can reverse direction due to particle losses.

Dissipation can enhance the critical current.

Spin-selective losses induce spin supercurrents and reversals.

Abstract

We show that supercurrent properties in a superfluid or superconducting junction are significantly modified due to single-particle losses present in a conduction channel. In the presence of a spin-independent particle loss, we find regimes where the Josephson current $I_N(\phi)$ takes zero at a position in between $\phi= 0$ and $\phi=\pi$, and the direction of the supercurrent is reversed. Although the region is narrow, we also find a regime in which the critical current is enhanced by dissipation. Such anomalous behaviors in the Josephson current are attributed to a subtle interplay between the contribution that is present regardless of dissipation and the unconventional one that is absent without dissipation. In the presence of a spin-selective particle loss, it is shown that a dissipation-induced spin supercurrent and its reversal occur. The proposed system is analyzed by means of the Keldysh field theory approach based on the Gorini-Kossakowski-Sudershan-Lindblad master equation and may be realized in ultracold atomic gases and solid-state systems.