Effect of fluctuations on the superfluid-supersolid phase transition on the lattice

TL;DR

This paper develops a theoretical framework to analyze how fluctuations influence the superfluid-supersolid phase transition in an extended Bose-Hubbard model on arbitrary lattices, revealing fluctuation-induced phenomena like negative superfluid densities and unstable states.

Contribution

It introduces a controlled expansion method incorporating fluctuations beyond mean field for the extended Bose-Hubbard model on arbitrary lattices, providing new insights into phase transition behavior.

Findings

Fluctuations cause negative superfluid densities near criticality.

Thermodynamical instability of the superfluid phase is observed.

Existence of long-lived supercooled states with large quantum fluctuations.

Abstract

We derive a controlled expansion into mean field plus fluctuations for the extended Bose-Hubbard model, involving interactions with many neighbors on an arbitrary periodic lattice, and study the superfluid-supersolid phase transition. Near the critical point, the impact of (thermal and quantum) fluctuations on top of the mean field grows, which entails striking effects, such as negative superfluid densities and thermodynamical instability of the superfluid phase -- earlier as expected from mean-field dynamics. We also predict the existence of long-lived "supercooled" states with anomalously large quantum fluctuations.