Stabilizing Topological Superfluidity of Lattice Fermions

TL;DR

This paper proposes adding a longer-range repulsion to lattice fermions to stabilize topological superfluidity, significantly enlarging the stable phase region and increasing the critical temperature, thus aiding experimental realization.

Contribution

Introducing a weaker longer-range repulsion stabilizes topological superfluidity in lattice fermions, overcoming phase separation issues and enhancing critical temperature.

Findings

Longer-range repulsion suppresses phase separation.

Stable topological superfluid phase is significantly enlarged.

Critical temperature increases by an order of magnitude.

Abstract

Attractive interaction between spinless fermions in a two-dimensional lattice drives the formation of a topological superfluid. But the topological phase is dynamically unstable towards phase separation when the system has a high density of states and large interaction strength. This limits the critical temperature to an experimentally challenging regime where, for example, even ultracold atoms and molecules in optical lattices would struggle to realize the topological superfluid. We propose that the introduction of a weaker longer-range repulsion, in addition to the short-range attraction between lattice fermions, will suppress the phase separation instability. Taking the honeycomb lattice as an example, we show that our proposal significantly enlarges the stable portion of the topological superfluid phase and increases the critical temperature by an order of magnitude. Our work opens a route to enhance the stability of topological superfluids by engineering inter-particle interactions.