Bose-Einstein condensation of deconfined spinons in two dimensions

TL;DR

This paper provides evidence for Bose-Einstein condensation of deconfined spinons in a two-dimensional quantum magnet under a magnetic field, revealing a new state of matter with fractionalized excitations.

Contribution

It introduces the concept of spinon Bose-Einstein condensation in a 2D system and combines quantum Monte Carlo simulations with field theory analysis to support this.

Findings

Evidence for spinon Bose-Einstein condensation under magnetic field

Identification of a temperature regime dominated by spinon interactions

Demonstration of deconfined spinons as fractionalized excitations

Abstract

The transition between the N\'{e}el antiferromagnet and the valence-bond solid state in two dimensions has become a paradigmatic example of deconfined quantum criticality, a non-Landau transition characterized by fractionalized excitations (spinons). We consider an extension of this scenario whereby the deconfined spinons are subject to a magnetic field. The primary purpose is to identify the exotic scenario of a Bose-Einstein condensate of spinons. We employ quantum Monte Carlo simulations of the \mbox{$J$-$Q$} model with a magnetic field and perform a quantum field theoretic analysis of the magnetic field and temperature dependence of thermodynamic quantities. The combined analysis provides compelling evidence for the Bose-Einstein condensation of spinons and also demonstrates an extended temperature regime in which the system is best described as a gas of spinons interacting with an emergent gauge field.