Vacancy-assisted superfluid drag

TL;DR

This paper investigates superfluid drag in a two-component Bose-Hubbard model with strong repulsion, revealing how hole-mediated transport induces dissipationless coupling between components, supported by analytic and numerical results.

Contribution

It provides a new analytic expression for superfluid coupling mediated by holes in the strongly interacting Bose-Hubbard model, verified through numerical simulations.

Findings

Strong dissipationless coupling between components due to hole motion

Derived a closed-form expression for superfluid drag in various lattices

Confirmed theoretical predictions with numerical simulations

Abstract

We study superfluid drag in the two-component Bose-Hubbard model with infinitely strong repulsive interactions. In this system, all transport is mediated by the motion of empty sites, or ``holes", and it is hard to move one component without moving the other. We demonstrate, with a combination of analytic and numeric techniques, that the motion of holes leads to strong dissipationless coupling between currents in the two components. This behavior is attributable to polaronic correlations that emerge in the presence of spin currents, which can be observed in experiments. We derive a closed-form expression for the coupling on various lattices in arbitrary spatial dimensions, which we verify through numerical simulations on two dimensional lattices.