Thermally induced metallic phase in a gapped quantum spin liquid - a Monte Carlo study of the Kitaev model with parity projection

TL;DR

This study demonstrates that increasing temperature can induce a metallic phase in a gapped quantum spin liquid, using an exact Monte Carlo method to analyze the Kitaev model and revealing potential experimental signatures of thermal metal behavior.

Contribution

We introduce a new Monte Carlo approach that accounts for parity projection, enabling the study of finite temperature effects and thermal metal phases in the Kitaev model.

Findings

Insulating phase becomes metallic at finite temperature

Energy distribution diverges logarithmically at low energies

Wave functions exhibit criticality similar to Anderson transitions

Abstract

Thermalisation is a probabilistic process. As such, it is generally expected that when we increase the temperature of a system its classical behaviour dominates its quantum coherences. By employing the Gibbs state of a translationally invariant quantum spin liquid - Kitaev's honeycomb lattice model - we demonstrate that an insulating phase at $T=0$ becomes metallic purely by increasing temperature. In particular, we compute the finite temperature distribution of energies and show that it diverges logarithmically, as we move to small energies. The corresponding wave functions become critical alike as at Anderson transitions. These characteristics are obtained within a new exact Monte Carlo method that simulates the finite temperature behaviour of the Kitaev model. In particular, we take into account the projection onto the physical parity sectors, required for identifying the topological degeneracy of the model. Our work opens the possibility to detect thermal metal behaviour in spin liquid experiments.