Supercurrent and dynamical instability of spin-orbit-coupled ultracold Bose gases

TL;DR

This paper studies the stability of supercurrents in spin-orbit-coupled Bose-Einstein condensates, revealing conditions for dynamical and energetic instabilities due to negative effective mass and lack of Galilean invariance.

Contribution

It provides a detailed analysis of supercurrent stability in spin-orbit-coupled BECs, highlighting the roles of dynamical and energetic instabilities and their experimental implications.

Findings

Supercurrents can become dynamically unstable in the plane-wave phase.

Dynamical instability is linked to complex sound velocity and negative effective mass.

Both instabilities can be experimentally induced via collective dipole oscillations.

Abstract

We investigate the stability of supercurrents in a Bose-Einstein condensate with one-dimensional spin-orbit and Raman couplings. The consequence of the lack of Galilean invariance is explicitly discussed. We show that in the plane-wave phase, characterized by a uniform density, the supercurrent state can become dynamically unstable, the instability being associated with the occurrence of a complex sound velocity, in a region where the effective mass is negative. We also discuss the emergence of energetic instability in these supercurrent states. We argue that both the dynamical and the energetic instabilities in these systems can be generated experimentally through excitation of the collective dipole oscillation.