Topological superradiant state in Fermi gases with cavity induced spin-orbit coupling

TL;DR

This paper investigates a topological superradiant state in a Fermi gas within an optical cavity, revealing how cavity-induced interactions induce topological phase transitions and analyzing the robustness and signatures of this exotic state.

Contribution

It provides a detailed characterization of the topological superradiant state, emphasizing the role of cavity-induced interband coupling in phase transitions and exploring the interplay between pairing and superradiance.

Findings

Cavity-induced interband coupling drives topological phase transition.

Signatures of topological transition observed in cavity field measurements.

Robustness of the topological superradiant state analyzed under various conditions.

Abstract

Coherently driven atomic gases inside optical cavities hold great promise for generating rich dynamics and exotic states of matter. It was shown recently that an exotic topological superradiant state exists in a two-component degenerate Fermi gas coupled to a cavity, where local order parameters coexist with global topological invariants. In this work, we characterize in detail various properties of this exotic state, focusing on the feedback interactions between the atoms and the cavity field. In particular, we demonstrate that cavity-induced interband coupling plays a crucial role in inducing the topological phase transition between the conventional and topological superradiant states. We analyze the interesting signatures in the cavity field left by the closing and reopening of the atomic bulk gap across the topological phase boundary and discuss the robustness of the topological superradiant state by investigating the steady-state phase diagram under various conditions. Furthermore, we consider the interaction effect and discuss the interplay between the pairing order in atomic ensembles and the superradiance of the cavity mode. Our work provides many valuable insights into the unique cavity--atom hybrid system under study and is helpful for future experimental exploration of the topological superradiant state.