Phase separation in supersolids

TL;DR

This paper investigates quantum phase transitions in a 2D hard-core boson Hubbard model, revealing that the commonly believed checkerboard supersolid is unstable, while a striped supersolid is stable and separated from the superfluid phase by a continuous transition.

Contribution

The study provides the first numerical evidence that the checkerboard supersolid is thermodynamically unstable and identifies a stable striped supersolid phase in the model.

Findings

Checkerboard supersolid is thermodynamically unstable.

Striped supersolid is thermodynamically stable.

Striped supersolid transitions smoothly to superfluid phase.

Abstract

We study quantum phase transitions in the ground state of the two dimensional hard-core boson Hubbard Hamiltonian. Recent work on this and related models has suggested ``supersolid'' phases with simultaneous diagonal and off-diagonal long range order. We show numerically that, contrary to the generally held belief, the most commonly discussed ``checkerboard'' supersolid is thermodynamically unstable. Furthermore, this supersolid cannot be stabilized by next near neighbour interaction. We obtain the correct phase diagram using the Maxwell construction. We demonstrate the ``striped'' supersolid is thermodynamically stable and is separated from the superfluid phase by a continuous phase transition.