Quantum Phase Transitions of Hard-Core Bosons in Background Potentials

TL;DR

This paper investigates quantum phase transitions of hard-core bosons in two dimensions under various background potentials, revealing different universality classes and critical exponents for each case.

Contribution

It provides a comparative analysis of phase transitions in hard-core bosons with staggered, uniform, and random potentials, identifying distinct universality classes and critical exponents.

Findings

Staggered potential transition belongs to XY universality class.

Uniform potential induces a mean field transition.

Disorder-driven transition exhibits unique critical exponents: z~1.4, ν~1, β~0.6.

Abstract

We study the zero temperature phase diagram of hard core bosons in two dimensions subjected to three types of background potentials: staggered, uniform, and random. In all three cases there is a quantum phase transition from a superfluid (at small potential) to a normal phase (at large potential), but with different universality classes. As expected, the staggered case belongs to the XY universality, while the uniform potential induces a mean field transition. The disorder driven transition is clearly different from both; in particular, we find z~1.4, \nu~1, and \beta~0.6.