Artificial Staggered Magnetic Field for Ultracold Atoms in Optical Lattices

TL;DR

This paper explores how an artificial staggered magnetic field in optical lattices influences ultracold atoms, revealing tunable Dirac fermions and diverse superfluid phases with distinct experimental signatures.

Contribution

It introduces a method to generate a staggered magnetic field in optical lattices and analyzes its effects on fermionic and bosonic atoms, including phase transitions and experimental detection.

Findings

Dirac cones are tunable by external flux.

Multiple superfluid phases are realized depending on flux.

Phase diagram of superfluid-Mott insulator transition is mapped.

Abstract

A time-dependent optical lattice with staggered particle current in the tight-binding regime was considered that can be described by a time-independent effective lattice model with an artificial staggered magnetic field. The low energy description of a single-component fermion in this lattice at half-filling is provided by two copies of ideal two-dimensional massless Dirac fermions. The Dirac cones are generally anisotropic and can be tuned by the external staggered flux $\p$. For bosons, the staggered flux modifies the single-particle spectrum such that in the weak coupling limit, depending on the flux $\p$, distinct superfluid phases are realized. Their properties are discussed, the nature of the phase transitions between them is establised, and Bogoliubov theory is used to determine their excitation spectra. Then the generalized superfluid-Mott-insulator transition is studied in the presence of the staggered flux and the complete phase diagram is established. Finally, the momentum distribution of the distinct superfluid phases is obtained, which provides a clear experimental signature of each phase in ballistic expansion experiments.