Staggered-Vortex Superfluid of Ultracold Bosons in an Optical Lattice

TL;DR

This paper explores a new phase of ultracold bosons in optical lattices, revealing a staggered-vortex superfluid with unique properties and extending findings to fermionic systems with potential relevance to graphene and superconductors.

Contribution

It introduces a novel finite-momentum superfluid phase with staggered vortices in a Bose-Hubbard model under an effective magnetic field.

Findings

Discovery of a staggered-vortex superfluid phase.

Identification of a finite-momentum superfluid with staggered rotational flux.

Extension to fermionic atoms showing an anisotropic Dirac spectrum.

Abstract

We show that the dynamics of cold bosonic atoms in a two-dimensional square optical lattice produced by a bichromatic light-shift potential is described by a Bose-Hubbard model with an additional effective staggered magnetic field. In addition to the known uniform superfluid and Mott insulating phases, the zero-temperature phase diagram exhibits a novel kind of finite-momentum superfluid phase, characterized by a quantized staggered rotational flux. An extension for fermionic atoms leads to an anisotropic Dirac spectrum, which is relevant to graphene and high-$T_c$ superconductors.