Ferromagnetic and Nematic Non-Fermi Liquids in Spin-Orbit Coupled Two-Dimensional Fermi Gases

TL;DR

This paper investigates how two-dimensional fermionic systems with Rashba spin-orbit coupling develop non-Fermi liquid behavior and various liquid crystalline phases at low densities, depending on interaction range.

Contribution

It reveals the emergence of ferromagnetic and nematic non-Fermi liquid phases in spin-orbit coupled Fermi gases, highlighting the role of interaction range and collective mode scattering.

Findings

Ferromagnetic phase for short-range interactions

Nematic phase for dipolar interactions

Strong deviations from Fermi liquid theory at low densities

Abstract

We study the fate of a two-dimensional system of interacting fermions with Rashba spin-orbit coupling in the dilute limit. The interactions are strongly renormalized at low densities, and give rise to various fermionic liquid crystalline phases, including a spin-density wave, an in-plane ferromagnet, and a non-magnetic nematic phase, even in the weak coupling limit. The nature of the ground state in the low-density limit depends on the range of the interactions: for short range interactions it is the ferromagnet, while for dipolar interactions the nematic phase is favored. Interestingly, the ferromagnetic and nematic phases exhibit strong deviations from Fermi liquid theory, due to the scattering of the Fermionic quasi-particles off long-wavelength collective modes. Thus, we argue that a system of interacting fermions with Rashba dispersion is generically a non-Fermi liquid at low densities.