Ferromagnetic and nematic non-Fermi liquids in spin-orbit-coupled two-dimensional Fermi gases

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 nonmagnetic 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 quasiparticles 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.