Thermal conductivity of a weakly interacting Bose gas in quasi-one-dimension

TL;DR

This paper investigates how three-body interactions influence thermal conductivity in a quasi-one-dimensional Bose gas, revealing that they dominate over two-body interactions and providing exact calculations and numerical results for the weak-coupling regime.

Contribution

The study derives an exact expression for thermal conductivity considering both two- and three-body interactions, highlighting the dominance of three-body effects in quasi-one-dimensional Bose gases.

Findings

Thermal conductivity is dominated by three-body interactions.

Exact evaluation of the Kubo formula in the zero-frequency limit.

Numerical temperature dependence matches quantum Boltzmann predictions.

Abstract

Transport coefficients are typically divergent for quantum integrable systems in one dimension, such as a Bose gas with a two-body contact interaction. However, when a one-dimensional system is realized by confining bosons into a tight matter waveguide, an effective three-body interaction inevitably arises as leading perturbation to break the integrability. This fact motivates us to study the thermal conductivity of a Bose gas in one dimension with both two-body and three-body interactions. In particular, we evaluate the Kubo formula exactly to the lowest order in perturbation by summing up all contributions that are naively higher orders in perturbation but become comparable in the zero-frequency limit due to the pinch singularity. Consequently, a self-consistent equation for a vertex function is derived, showing that the thermal conductivity in quasi-one-dimension is dominated by the three-body interaction rather than the two-body interaction. Furthermore, the resulting thermal conductivity in the weak-coupling limit proves to be identical to that computed based on the quantum Boltzmann equation and its temperature dependence is numerically determined.