Thermodynamics of a gas of deconfined bosonic spinons in two dimensions

TL;DR

This paper models the thermodynamics of deconfined bosonic spinons at a quantum critical point in two-dimensional antiferromagnets, deriving specific heat and susceptibility expressions that match quantum Monte Carlo results.

Contribution

It introduces a theoretical framework for the thermodynamics of deconfined spinons, including a confinement length scale, and validates it against numerical simulations.

Findings

Excellent agreement with quantum Monte Carlo data

Logarithmic correction in susceptibility explained by confinement length scale

Confinement length scales with temperature as xi^(1+a)

Abstract

We consider the quantum phase transition between a Neel antiferromagnet and a valence-bond solid (VBS) in a two-dimensional system of S=1/2 spins. Assuming that the excitations of the critical ground state are linearly dispersing deconfined spinons obeying Bose statistics, we derive expressions for the specific heat and the magnetic susceptibility at low temperature T. Comparing with quantum Monte Carlo results for the J-Q model, which is a candidate for a deconfined Neel-VBS transition, we find excellent agreement, including a previously noted logarithmic correction in the susceptibility. In our treatment, this is a direct consequence of a confinement length scale Lambda which is proportional to the correlation length xi raised to a non-trivial power; Lambda ~ xi^(1+a) ~1/T^(1+a), with a>0 (with a approximately 0.2 in the model).