Dynamical structure factor of one-dimensional Bose gases: experimental signatures of beyond-Luttinger liquid physics

TL;DR

This study investigates the dynamical structure factor of strongly-interacting 1D Bose gases, revealing signatures of beyond-Luttinger liquid physics through experimental measurements aligned with Lieb-Liniger model predictions.

Contribution

The paper provides the first experimental observation of interaction-induced excitations in 1D Bose gases that go beyond traditional Luttinger liquid theory.

Findings

Experimental evidence of beyond-Luttinger liquid excitations

Spectral widths dominated by interaction-induced dynamics

Agreement with Lieb-Liniger model predictions at finite temperature

Abstract

Interactions are known to have dramatic effects on bosonic gases in one dimension (1D). Not only does the ground state transform from a condensate-like state to an effective Fermi sea, but new fundamental excitations, which do not have any higher-dimensional equivalents, are predicted to appear. In this work, we trace these elusive excitations via their effects on the dynamical structure factor of 1D strongly-interacting Bose gases at low temperature. An array of 1D Bose gases is obtained by loading a $^{87}$Rb condensate in a 2D lattice potential. The dynamical structure factor of the system is probed by energy deposition through low-momentum Bragg excitations. The experimental signals are compared to recent theoretical predictions for the dynamical structure factor of the Lieb-Liniger model at $T > 0$. Our results demonstrate that the main contribution to the spectral widths stems from the dynamics of the interaction-induced excitations in the gas, which cannot be described by the Luttinger liquid theory.