Damping of phonons in one-dimensional quantum fluids

TL;DR

This study investigates phonon damping in weakly interacting one-dimensional quantum fluids, revealing unexpected rapid damping in the linear regime and nonlinear wave breaking at higher excitations, advancing understanding of quantum many-body relaxation.

Contribution

It provides the first direct experimental observation of phonon damping in 1D Bose gases and confirms theoretical predictions of non-analytic scaling behavior.

Findings

Fast damping in linear response regime matches theoretical predictions.

Crossover to nonlinear wave breaking observed at higher excitations.

Results clarify phonon behavior and relaxation in 1D quantum fluids.

Abstract

Collective excitations in one-dimensional (1D) quantum fluids are expected to propagate almost without dissipation. Here we directly excite phonon modes in a weakly interacting 1D Bose gas and study their time evolution. In the linear response regime, damping is surprisingly fast and quantitatively follows the non-analytic scaling predicted by Andreev's hydrodynamic description. For stronger excitations, we observe a crossover to a highly nonlinear regime characterized by wave breaking, captured by the finite-temperature nonlinear Schr\"odinger evolution. Our results resolve a long-standing question on the fate of phonons in 1D Bose gases, and open new pathways to study non-linear relaxation in quantum many-body systems.