Japaridze, George I.

Date: Friday, November 13, 2015
Time: 14:00
Place: ETH Zurich, Hönggerberg, HIT K52
Host: Tilman Esslinger, Michael Messer

Ultracold fermions in a one-dimensional bipartite optical lattice: Metal-insulator transitions driven by shaking

George  I. Japaridze
Ilia State University and Andronikashvili Institute of Physics, Tbilisi, Georgia

The behavior of a system of fermionic atoms loaded in a bipartite one-dimensional optical lattice that is under the action of an external time-periodic driving force is studied. By using Floquet theory, an effective model is derived. The bare hopping coefficients are renormalized by zeroth-order Bessel functions of the first kind with different arguments for the nearest-neighbor and next-nearest-neighbor 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. We investigate the effect of on-site Hubbard interactions on the four-Fermi-point metal-insulator 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 Luther-Emery liquid (spin-gapped metal) for both repulsive and attractive interactions, contrary to the usual Hubbard model, which exhibits a Mott-insulator phase for repulsive interactions.