Landau critical velocity in weakly interacting Bose gases

TL;DR

This paper investigates how superfluidity in weakly interacting Bose gases persists with decreased superfluid density when flow exceeds the Landau critical velocity, especially considering finite-range interactions.

Contribution

It explicitly constructs the non-uniform condensate for flows above the critical velocity and quantifies the resulting decrease in superfluid density.

Findings

Flow above v_c reduces superfluid density without destroying superfluidity.

Constructs the non-uniform condensate profile for superfluid flow beyond v_c.

Provides insights relevant to solitons, vortices, and critical currents in related systems.

Abstract

The flow of a uniform Bose gas at speeds greater than the Landau critical velocity, v_c, does not necessarily destroy superfluidity, but rather need only lead to a decrease of the superfluid mass density, {\rho}_s. Analyzing a weakly interacting Bose gas with a finite range interparticle interaction that leads to a Landau critical velocity at non-zero quasiparticle momentum, we explicitly construct the (non-uniform) condensate for fluid flow faster than v_c and calculate the accompanying decrease in {\rho}_s. We briefly comment on the relation of the physics to other problems in superfluids, e.g., solitons, and vortices in Bose-Einstein condensates, and critical currents in superconductors.