Non-Equilibrium Enhancement of Superfluidity in a Bose-Hubbard Model

Andrew J. Robertson, Victor M. Galitski

Malcolm P. Kennett, Matthew Fitzpatrick

Stephan Langer, Andrew J. Daley

Florian R. Bär, Malcolm P. Kennett

We study the out-of-equilibrium dynamics of the Bose-Hubbard model for two-component bosons using a strong-coupling approach within the closed-time-path formalism and develop an effective theory for the action of this problem. We obtain equations of motion for the superfluid order parameters of both boson species for both the superfluid and Mott-insulating phases and study these in the low-frequency, long-wavelength limit during a quantum quench for various initial conditions. We find that an additional degree of freedom for bosons leads to a richer phase diagram and out-of-equilibrium dynamics than the single-component situation.

Gabrielle Roberts, Brendan Saxberg, Andrei Vrajitoarea +4 more

Matthew Fitzpatrick, Malcolm P. Kennett

We develop a formalism that allows the study of correlations in space and time in both the superfluid and Mott insulating phases of the Bose–Hubbard Model. Specifically, we obtain a two particle irreducible effective action within the contour-time formalism that allows for both equilibrium and out of equilibrium phenomena. We derive equations of motion for both the superfluid order parameter and two-point correlation functions. To assess the accuracy of this formalism, we study the equilibrium solution of the equations of motion and compare our results to existing strong coupling methods as well as exact methods where possible. We discuss applications of this formalism to out of equilibrium situations.