Spin-charge separation in a 1D Fermi gas with tunable interactions

TL;DR

This study demonstrates spin-charge separation in a one-dimensional Fermi gas with tunable interactions, confirming Tomonaga-Luttinger liquid theory through Bragg spectroscopy measurements of excitation velocities.

Contribution

First direct experimental observation of spin-charge separation in a tunable 1D Fermi gas using Bragg spectroscopy, aligning with theoretical predictions.

Findings

Spin and charge velocities shift oppositely with interaction strength.

Excitation spectra agree quantitatively with Tomonaga-Luttinger liquid theory.

Spin excitations become dispersive at large interactions, indicating nonlinear effects.

Abstract

Ultracold atoms confined to periodic potentials have proven to be a powerful tool for quantum simulation of complex many-body systems. We confine fermions to one-dimension to realize the Tomonaga-Luttinger liquid model describing the highly collective nature of their low-energy excitations. We use Bragg spectroscopy to directly excite either the spin or charge wave for various strength of repulsive interaction. We observe that the velocity of the spin and charge excitations shift in opposite directions with increasing interaction, a hallmark of spin-charge separation. The excitation spectra are in quantitative agreement with the Tomonaga-Luttinger liquid theory, and furthermore, we find that the spin excitations become dispersive at large interaction, signaling the onset of the nonlinear Luttinger liquid regime.