Valley-dependent gauge fields for ultracold atoms in square optical superlattices

Abstract

We propose an experimental scheme to realize the valley-dependent gauge fields for ultracold fermionic atoms trapped in a state-dependent square optical lattice. Our scheme relies on two sets of Raman laser beams to engineer the hopping between adjacent sites populated by two-component fermionic atoms. One set of Raman beams is used to realize a staggered π-flux lattice, where low-energy atoms near two inequivalent Dirac points should be described by the Dirac equation for spin-12 particles. Another set of laser beams with proper Rabi frequencies is added to further modulate the atomic hopping parameters. The hopping modulation will give rise to effective gauge potentials with opposite signs near the two valleys, mimicking the interesting strain-induced pseudogauge fields in graphene. The proposed valley-dependent gauge fields are tunable and provide an alternative route to realize an uncommon type of quantum Hall effects and atomic devices. © 2014 American Physical Society.