Ultracold fermions in a onedimensional bipartite optical lattice: Metalinsulator transitions driven by shaking
Abstract
We theoretically investigate the behavior of a system of fermionic atoms loaded in a bipartite onedimensional optical lattice that is under the action of an external timeperiodic driving force. By using Floquet theory, an effective model is derived. The bare hopping coefficients are renormalized by zerothorder Bessel functions of the first kind with different arguments for the nearestneighbor and nextnearestneighbor hopping. The insulating behavior characterizing the system at half filling in the absence of driving is dynamically suppressed, and for particular values of the driving parameter the system becomes either a standard metal or an unconventional metal with four Fermi points. The existence of the fourFermipoint metal relies on the fact that, as a consequence of the shaking procedure, the nextnearestneighbor hopping coefficients become significant compared to the nearestneighbor ones. We use the bosonization technique to investigate the effect of onsite Hubbard interactions on the fourFermipoint metalinsulator phase transition. Attractive interactions are expected to enlarge the regime of parameters where the unconventional metallic phase arises, whereas repulsive interactions reduce it. This metallic phase is known to be a LutherEmery liquid (spingapped metal) for both repulsive and attractive interactions, contrary to the usual Hubbard model, which exhibits a Mottinsulator phase for repulsive interactions. Ultracold fermions in driven onedimensional bipartite optical lattices provide an interesting platform for the realization of this longstudied fourFermipoint unconventional metal.
 Publication:

Physical Review A
 Pub Date:
 August 2014
 DOI:
 10.1103/PhysRevA.90.023634
 arXiv:
 arXiv:1405.4756
 Bibcode:
 2014PhRvA..90b3634D
 Keywords:

 67.85.Lm;
 71.10.Pm;
 71.30.+h;
 Degenerate Fermi gases;
 Fermions in reduced dimensions;
 Metalinsulator transitions and other electronic transitions;
 Condensed Matter  Quantum Gases
 EPrint:
 11 pages, 6 figures