Trimer superfluid induced by photoassociation on the state-dependent optical lattice

What is it about?

We use the mean-field method, the Quantum Monte-carlo method and the Density matrix renormalization group method to study the trimer superfluid phase and the quantum phase diagram of the Bose-Hubbard model in an optical lattice, with explicit trimer tunneling term. Theoretically, we derive the explicit trimer hopping terms, such as a_i^{3 \dagger} a_j^3, by the Schrieffer-Wolf transformation. In practice, the trimer superfluid described by these terms is driven by photoassociation. Without the on-site interaction, the phase transition between the trimer superfluid phase and the Mott Insulator phase is continuous. Turning on the on-site interaction, the phase transition are first order with Mott insulators of atom filling \rho =1 and \rho=2. With nonzero atom tunneling, the phase transition is first order from the atomsuperfluid to the trimer superfluid. The vorticity is 1/3 for the trimer superfluid. The power law decay exponents is 1/2 for the non diagonal correlation a_i^{\dagger 3} a_j^3, i.e. the same as the exponent of the correlation a_i^{\dagger} a_j in hardcore bosons. The density dependent atom-tunneling term n_i^2 a_i^{\dagger} a_j and pair tunneling term n_i a_i^{\dagger 2} a_j^2 are also studied. With these terms, the phase transition from the empty phase to atom superfluid is first order, different from the cases without the density dependent terms. The phase transition is still first order from the trimer superfluid phase to the atom superfluid. The effects of temperature are studied and the boundary lines of Berezinskii-Kosterlitz-Thouless phase transitions are also given. Our results will be helpful to realize the trimer superfluid by the cold atom experiment.

Featured Image

Why is it important?

Again this work makes use of the mean-field Bose-Hubbard model applied to Supefluids. Our results will be helpful to guide the optical experiments to realize the trimer superfluid.

Perspectives