Magnetic orders in a Fermi gas induced by cavity-field fluctuations

TL;DR

This paper explores how cavity-field fluctuations induce various magnetic orders in a one-dimensional Fermi gas, revealing phase transitions outside the superradiant regime driven by photonless cavity fluctuations.

Contribution

It introduces a numerical study of magnetic orders in a Fermi gas with cavity-assisted Raman couplings, highlighting phase transitions driven by cavity-field fluctuations.

Findings

Magnetic orders are induced by cavity-field fluctuations without mean photon presence.

Phase diagram includes transitions outside the superradiant regime.

Long-range interactions compete with on-site interactions to produce diverse magnetic phases.

Abstract

We study magnetic orders of fermions under cavity-assisted Raman couplings in a one-dimensional lattice at half filling. The cavity-enhanced atom-photon coupling introduces a dynamic long-range interaction between the fermions, which competes with the short-range on-site interaction and leads to a variety of magnetic orders. Adopting a numerical density-matrix-renormalization-group method, we investigate the various magnetic orders and map out the steady-state phase diagram. Interestingly, as all the phase transitions take place outside the superradiant regime, the magnetic orders are associated with cavity-field fluctuations with a vanishing number of photons on the mean-field level.