Competing order in two-band Bose-Hubbard chains with extended-range interactions

TL;DR

This paper theoretically explores a two-band Bose-Hubbard chain with extended interactions, revealing conditions under which supersolid phases emerge from the competition between density wave, superfluid, and Mott insulating orders.

Contribution

It introduces a novel scenario where supersolid order arises from the interplay of density wave and superfluid phases in a two-band Bose-Hubbard system with extended interactions.

Findings

Supersolid order can emerge from the coexistence of density wave and superfluid phases.

The phase diagram includes competition between supersolidity, phase separation, superfluidity, and Mott insulators.

A potential experimental setup involving a lower density-wave supporting band and a thermally excited superfluid band is proposed.

Abstract

Motivated by the recent progress in realizing and controlling extended Bose-Hubbard systems using excitonic or atomic devices, the present Letter theoretically investigates the case of a two-band Bose-Hubbard chain with nearest-neighbor interactions. Specifically, this study concentrates on the scenario where, due to the interactions, one band supports a density wave phase, i.e. a correlated insulating phase with spontaneous breaking of translational symmetry in the lattice, while the other band supports superfluid behavior. Using the density matrix renormalization group method, we show that supersolid order can emerge from such a combination, that is, an elusive quantum state that combines crystalline order with long-range phase coherence. Depending on the filling of the bands and the interband interaction strength, the supersolid phase competes with phase-separation, superfluid order, or Mott insulating density-wave order. As a possible setup to observe supersolidity, we propose the combination of a lower band supporting density-wave order and a thermally excited band that supports superfluidity due to weaker lattice confinement.