Supersolid state of ultracold fermions in an optical lattice

TL;DR

This paper demonstrates that a supersolid state, combining superfluidity and density-wave order, can be stabilized in ultracold fermionic atoms in an optical lattice, especially due to the influence of a confining potential.

Contribution

It reveals that a confining potential is crucial for stabilizing the supersolid state in fermionic optical lattices, providing a detailed phase diagram of competing phases.

Findings

Supersolid state coexists with density-wave and superfluid phases.

Confining potential stabilizes the supersolid state.

Rich phase diagram with domain structures at low temperatures.

Abstract

We study ultracold fermionic atoms trapped in an optical lattice with harmonic confinement by means of the dynamical mean-field approximation. It is demonstrated that a supersolid state, where an s-wave superfluid coexists with a density-wave state with a checkerboard pattern, is stabilized by attractive onsite interactions on a square lattice. Our new finding here is that a confining potential plays an invaluable role in stabilizing the supersolid state. We establish a rich phase diagram at low temperatures, which clearly shows how the insulator, the density wave and the superfluid compete with each other to produce an intriguing domain structure. Our results shed light on the possibility of the supersolid state in fermionic optical lattice systems.