Interplay of quantum and thermal fluctuations in a frustrated magnet

TL;DR

This paper investigates how thermal and quantum fluctuations interact in a frustrated magnet, revealing an extended critical phase and phase transitions, supported by quantum Monte Carlo simulations, with implications for quantum criticality and phase stability.

Contribution

It uncovers an extended critical phase in a frustrated magnet driven by both thermal and quantum fluctuations, and maps its phase diagram using quantum Monte Carlo methods.

Findings

Identification of an extended critical phase

Observation of two Kosterlitz-Thouless transitions

Confirmation of 3d XY universality class for quantum phase transition

Abstract

We demonstrate the presence of an extended critical phase in the transverse field Ising magnet on the triangular lattice, in a regime where both thermal and quantum fluctuations are important. We map out a complete phase diagram by means of quantum Monte Carlo simulations, and find that the critical phase is the result of thermal fluctuations destabilising an order established by the quantum fluctuations. It is separated by two Kosterlitz-Thouless transitions from the paramagnet on one hand and the quantum-fluctuation driven three-sublattice ordered phase on the other. Our work provides further evidence that the zero temperature quantum phase transition is in the 3d XY universality class.