Finite-momentum Bose-Einstein condensates in shaken two-dimensional square optical lattices

Abstract

We consider ultracold bosons in a 2D square optical lattice described by the Bose-Hubbard model. In addition, an external time-dependent sinusoidal force is applied to the system, which shakes the lattice along one of the diagonals. The effect of the shaking is to renormalize the nearest-neighbor hopping coefficients, which can be arbitrarily reduced, can vanish, or can even change sign, depending on the shaking parameter. It is therefore necessary to account for higher-order hopping terms, which are renormalized differently by the shaking, and introduce anisotropy into the problem. We show that the competition between these different hopping terms leads to finite-momentum condensates, with a momentum that may be tuned via the strength of the shaking. We calculate the boundaries between the Mott-insulator and the different superfluid phases, and present the time-of-flight images expected to be observed experimentally. Our results open up new possibilities for the realization of bosonic analogs of the FFLO phase describing inhomogeneous superconductivity.

Generation of atypical hopping and interactions by kinetic driving

“…This finding has considerable implications for the observation of this state in experiment [40]. While a single measurement of the momentum distribution of a Fock state would yield an equal weight for the two momenta k=±π/2, the cat state would be collapsed to one momentum or the other with equal probability.…”

Expansion of Bose-Hubbard Mott insulators in optical lattices

“…Hence these systems can be used to create highly controllable atom lasers. Other nonequilibrium setups that allow one to obtain condensation at finite momentum [27,28] do not seem suitable for the latter purpose.…”

Towards large-Chern-number topological phases by periodic quenching

“…That is, we periodically set t 3 = 0.75 and φ = −π/6 for duration T 1 and then let t 3 = −0.75 and φ = −π/2 for duration T 2 . The changes in both t 3 and φ could be realized by modulating the optical lattice realizing the Haldane model [45,52,53]. Figure 1 shows the obtained PTPs.…”