Quantum phase transitions across p-wave Feshbach resonance

TL;DR

This paper investigates quantum phase transitions in a polarized Fermi gas across a p-wave Feshbach resonance, revealing a transition from p_x-wave to chiral p_x+ i p_y-wave superfluidity with topological properties.

Contribution

It demonstrates a magnetic field-tuned quantum phase transition between different p-wave superfluids, including a topological phase with non-Abelian excitations, in a polarized Fermi gas.

Findings

Transition from p_x-wave to p_x+i p_y-wave superfluid across Feshbach resonance

Identification of a topological phase with non-Abelian excitations in 2D

Spontaneous breaking of time-reversal symmetry in the superfluid state

Abstract

We study a single-species polarized Fermi gas tuned across a narrow p-wave Feshbach resonance. We show that in the course of a BEC-BCS crossover the system can undergo a magnetic field-tuned quantum phase transition from a p_x-wave to a p_x+i p_y-wave superfluid. The latter state, that spontaneously breaks time-reversal symmetry, furthermore undergoes a topological p_x+ i p_y to p_x+ i p_y transition at zero chemical potential \mu. In two-dimensions, for \mu>0 it is characterized by a Pfaffian ground state exhibiting topological order and non-Abelian excitations familiar from fractional quantum Hall systems.