Spin dynamics and Andreev-Bashkin effect in mixtures of one-dimensional Bose gases

TL;DR

This paper studies spin wave propagation in one-dimensional two-component Bose gases, revealing how interactions influence phase separation, spin-wave velocity, and the non-dissipative drag effect known as the Andreev-Bashkin effect.

Contribution

It provides a detailed quantum Monte Carlo analysis of ground-state properties and quantifies the Andreev-Bashkin drag effect in strongly interacting regimes.

Findings

Spin susceptibility and structure factor depend on coupling strengths.

Spin-wave velocity softens near phase separation.

Strong coupling suppresses spin-wave velocity due to drag effect.

Abstract

We investigate the propagation of spin waves in two-component mixtures of one-dimensional Bose gases interacting through repulsive contact potentials. By using quantum Monte Carlo methods we calculate static ground-state properties, such as the spin susceptibility and the spin structure factor, as a function of both the intra-species and inter-species coupling strength and we determine the critical parameters for phase separation. In homogeneous mixtures, results of the velocity of spin waves and of its softening close to the critical point of phase separation are obtained by means of a sum-rule approach. We quantify the non-dissipative drag effect, resulting from the Andreev-Bashkin current-current interaction between the two components of the gas, and we show that in the regime of strong coupling it causes a significant suppression of the spin-wave velocity.