Interference induced anisotropy in a two-dimensional dark state optical lattice

Traditionally, optical lattices are created by interfering light beams, trapping atoms at minima or maxima of the emerging interference pattern. Because the resulting potential follows the intensity of the optical field, its spatial structure is diffraction limited, limiting the lattice period to be no smaller than half the optical wavelength [1,2].



In this work we use the Lambda coupling scheme [3, 4, 5] with a control field containing two orthogonal standing waves (one of which is out-of-phase) to engineer a stwo-dimensional optical lattice with sub-wavelength characteristics by means of the geometric phase for the coherent dark state. By using two parameters: 1) the phase difference of the OOF standing wave, and 2) the amplitude ratio of the two orthogonal standing waves, one can control the tunneling parameters. The nonzero phase difference introduces a synthetic magnetic field which can be tuned to realize a weakly interacting tube model [6].