Non-equilibrium dynamics of long-range interacting Fermions

TL;DR

This paper studies the out-of-equilibrium growth of order in a Fermi gas with long-range interactions, revealing universal dynamics and insensitivity to contact interactions during a density-wave phase transition.

Contribution

It demonstrates the real-time exponential growth of the order parameter in a long-range interacting Fermi gas and shows its independence from contact interactions, extending understanding of non-equilibrium phase transition dynamics.

Findings

Order parameter grows exponentially and can exceed the Fermi energy.

Growth rate is insensitive to contact interaction strength.

Universal scaling behavior emerges despite strong microscopic interactions.

Abstract

A fundamental problem of out-of-equilibrium physics is the speed at which the order parameter grows upon crossing a phase transition. Here, we investigate the dynamics of ordering in a Fermi gas undergoing a density-wave phase transition induced by quenching of long-range, cavity-mediated interactions. We observe in real-time the exponential rise of the order parameter and track its growth over several orders of magnitude. Remarkably, the growth rate is insensitive to the contact interaction strength from the ideal gas up to the unitary limit and can exceed the Fermi energy by an order of magnitude, in quantitative agreement with a linearized instability analysis. We then generalize our results to linear interaction ramps, where deviations from the adiabatic behaviour are captured by a simple dynamical ansatz. Our study offers a paradigmatic example of the interplay between non-locality and non-equilibrium dynamics, where universal scaling behaviour emerges despite strong interactions at the microscopic level.