The phase diagram of two-dimensional fast-rotating ultra-cold fermionic atoms near unitarity

TL;DR

This paper explores the complex phase diagram of rapidly rotating ultra-cold fermionic atoms near unitarity, revealing various vortex and spin textures, and predicts experimental signatures of exotic superfluid phases.

Contribution

It introduces a unified theoretical framework for vortex lattices, FFLO states, and spin textures in rotating cold fermionic gases, highlighting their interplay and stability.

Findings

Hierarchy of spin-polarized and FFLO phases identified

Quantum fluctuations lead to vortex liquid states

Vortex lattices enhance FFLO state stability

Abstract

By analyzing vortex lattices, re-entrant Cooper pairing and Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) states in a single theoretical framework we explore how vortices and spin textures join to protect superconductivity against large magnetic fields. We use a rapidly rotating ultra-cold gas of fermionic atoms near unitarity as a model system amenable to experimental exploration, and discover a hierarchy of spin-polarized and FFLO phases in which a metal or a band-insulator of unpaired particles coexists with a spatially modulated superfluid hosting a vortex lattice. Quantum fluctuations can transform these phases into strongly correlated "vortex liquid" metals and insulators respectively. We argue that vortex lattices significantly enhance the stability of FFLO states and discuss prospects for observing these states in cold atom experiments.