Motion of an Impurity in a Bose-Einstein Condensate with Weyl Spin-Orbit Coupling: Non-collinear Drag Force and Anisotropic Critical Velocity

TL;DR

This paper investigates how a point impurity moves through a 3D Bose-Einstein condensate with Weyl spin-orbit coupling, revealing non-collinear drag forces and anisotropic critical velocities due to finite-momentum condensation.

Contribution

It introduces a linear-response analysis of impurity motion in a Weyl spin-orbit coupled BEC, highlighting non-collinear drag forces and anisotropic critical velocities as novel phenomena.

Findings

Drag force is generally not aligned with impurity velocity.

Critical velocity is anisotropic due to spin-orbit coupling.

Finite-momentum condensation causes unusual impurity dynamics.

Abstract

We consider the motion of a point-like impurity through a three-dimensional two-component Bose-Einstein condensate subject to Weyl spin-orbit coupling. Using linear-response theory, we calculate the drag force felt by the impurity and the associated anisotropic critical velocity from the spectrum of elementary excitations. The drag force is shown to be generally not collinear with the velocity of the impurity. This unusual behavior is a consequence of condensation into a finite-momentum state due to the spin-orbit coupling.