Weak first-order superfluid--solid quantum phase transitions

TL;DR

This paper investigates superfluid--solid quantum phase transitions in 2D lattice models, revealing they are generally weakly first-order with exceptions at high-symmetry points, and highlights the subtlety in distinguishing transition types in finite systems.

Contribution

The study provides evidence that superfluid--solid transitions are typically weak first-order and clarifies the conditions under which they appear continuous or high-symmetry, using Monte Carlo simulations.

Findings

Transitions are mostly weak first-order.

High-symmetry points require fine tuning.

Finite systems may misrepresent transition order.

Abstract

We study superfluid--solid zero-temperature transitions in two-dimensional lattice boson/spin models by Worm-Algorithm Monte Carlo simulations. We observe that such transitions are typically first-order with the exception of special high-symmetry points which require fine tuning in the Hamiltonian parameter space. We present evidence that the superfluid--checkerboard solid and superfluid--valence-bond solid transitions at half-integer filling factor are extremely weak first-order transitions and in small systems they may be confused with continuous or high-symmetry points.