Spinons and Spin-Charge Separation at the Deconfined Quantum Critical Point

TL;DR

This study uses advanced numerical methods to investigate spinon excitations and spin-charge separation at a quantum critical point in a 2D quantum magnet, revealing a broad continuum consistent with deconfined quantum criticality.

Contribution

It provides numerical evidence for spinon continua and spin-charge separation at the deconfined quantum critical point in the $J$-$Q$ model, supporting the fermionic $ ext{ extpi}$-flux state as an effective description.

Findings

Broad spinon continuum consistent with fermionic $ ext{ extpi}$-flux state

Evidence of spin-charge separation with holon propagation

Implication of an extended holon metal phase at finite doping

Abstract

Using quantum Monte Carlo and numerical analytic continuation methods, we study the dynamic spin structure factor and the single-hole spectral function of a two-dimensional quantum magnet ($J$-$Q$ model) at its quantum phase transition separating N\'eel antiferromagnetic and spontaneously dimerized ground states. At this putative deconfined quantum-critical point, we find a broad continuum of spinon excitations that can be accounted for by the fermionic $\pi$-flux state; a known mean-field model for deconfined quantum criticality. We find that the best description of the two-spinon continuum is with a version of the model with a $2\times 2$ unit cell, reflecting non-trivial mutual statistics of spinons and anti-spinons. The single-hole spectral function can be described by the same spinon dispersion relation and an independently propagating holon. Thus, the system exhibits spin-charge separation and will likely evolve into an extended holon metal phase at finite doping.