Striped states in weakly trapped ultracold Bose gases with Rashba spin-orbit coupling

TL;DR

This paper proposes a modified striped state for ultracold Bose gases with Rashba spin-orbit coupling in finite traps, which avoids unphysical boundary particle flow and has lower energy than the conventional state.

Contribution

A variational wave function for trapped systems that mimics striped states without boundary flow and is energetically favorable.

Findings

Modified striped state has lower energy than conventional state.

The state features a line of unquantized coreless vortices.

It provides a physically realistic description of striped states in finite traps.

Abstract

The striped state of ultracold bosons with Rashba spin-orbit coupling in a homogeneous infinite system has, as we show, a constant particle flow, which in a finite-size system would accumulate particles at the boundaries; it is thus not a physical steady state of the system. We propose, as a variational ansatz, a condensate wave function for a weakly trapped system which behaves similarly to the striped state near the center, but does not have particle flow at the boundaries. This state has a line of unquantized coreless vortices. We show, by minimizing the total energy, that our modified striped state has lower energy than the conventional striped state and it is thus a physically appropriate starting point to analyze striped states in finite systems.