Thermal Phase transitions in attractive extended Bose-Hubbard Model with three-body constraint

TL;DR

This paper uses quantum Monte Carlo simulations to explore the finite-temperature phase diagram of an attractive Bose-Hubbard model with a three-body constraint, revealing the nature of phase transitions between superfluid phases.

Contribution

It uncovers the first-order nature of symmetry-breaking transitions and identifies the Kosterlitz-Thouless transition with anomalous stiffness jump driven by fractional vortex unbinding.

Findings

First-order $Z_2$ symmetry-breaking transitions between superfluid phases.

Kosterlitz-Thouless transition with anomalous universal stiffness jump.

Transition driven by unbinding of fractional vortex pairs.

Abstract

By means of quantum Monte Carlo simulations implemented with a two-loop update scheme, the finite-temperature phase diagram of a three-body constrained attractive Bose lattice gas is investigated. The nature of the thermal phase transitions around the dimer superfluid and the atomic superfluid is unveiled. We find that the $Z_2$ symmetry-breaking transitions between these two superfluid phases are of first order even at nonzero temperatures. More interestingly, the thermal transition from the dimer superfluid to the normal fluid is found to be consistent with the Kosterlitz-Thouless type but giving an anomalous universal stiffness jump. It demonstrates that this transition is driven by unbinding of pairs of fractional vortices.