Quantum phase transitions of the diluted O(3) rotor model

TL;DR

This paper investigates the phase diagram and quantum phase transitions of a two-dimensional diluted O(3) quantum rotor model using large-scale Monte Carlo simulations, revealing finite-disorder fixed points and contrasting with other exotic scaling scenarios.

Contribution

It provides the first detailed analysis of the critical behavior of the diluted O(3) quantum rotor model, identifying finite-disorder fixed points for both transitions.

Findings

Both transitions are characterized by finite-disorder fixed points with power-law scaling.

The study distinguishes the behavior of the generic transition and the percolation transition.

Results relate to classification of phase transitions with quenched disorder and implications for disordered quantum magnets.

Abstract

We study the phase diagram and the quantum phase transitions of a site-diluted two-dimensional O(3) quantum rotor model by means of large-scale Monte-Carlo simulations. This system has two quantum phase transitions, a generic one for small dilutions, and a percolation transition across the lattice percolation threshold. We determine the critical behavior for both transitions and for the multicritical point that separates them. In contrast to the exotic scaling scenarios found in other random quantum systems, all these transitions are characterized by finite-disorder fixed points with power-law scaling. We relate our findings to a recent classification of phase transitions with quenched disorder according to the rare region dimensionality, and we discuss experiments in disordered quantum magnets.