Observe novel tricritical phenomena in self-organized Fermi gas induced by higher order Fermi surface nesting

TL;DR

This paper explores how higher-order Fermi surface nesting induces novel tricritical phenomena and multistability in self-organized Fermi gases within optical lattices, revealing complex phase transition behaviors at finite temperatures.

Contribution

It uncovers the role of higher-order Fermi surface nesting in tricritical phenomena and demonstrates the coexistence of quantum and classical tricritical points in finite-temperature Fermi gases.

Findings

Tricritical point arises from higher-order Fermi surface nesting.

Both quantum- and classical-type tricritical phenomena can occur simultaneously.

An optimal temperature exists for observing superradiance.

Abstract

Cold atom systems in optical lattices have long been recognized as an ideal platform for bridging condense matter physics and quantum optics. Here, we investigate the 1D fermionic superradiance in an optical lattice, and observe novel tricritical phenomena and multistability in finite-temperature cases. As a starting point, which can be analytically calculated, we compare the 1D and 2D Fermi gases in zero-temperature limit. It turns out that the tricritical point originates from the higher-order Fermi surface nesting (FSN), and the infrared divergence in 1D systems is absent in 2D cases. When extending to finite-temperature cases, our numerical results reveal that both quantum- and classical-type trcritical phenomena can be observed simultaneously. Moreover, there exists an optimal temperature for observing superradiance. This work provides a new approach to understanding the relation between quantum and classical phase transitions.