Dynamical Signature of Fractionalization at the Deconfined Quantum Critical Point

TL;DR

This study uses large-scale quantum Monte Carlo simulations to identify distinctive dynamical signatures of fractionalized excitations at a deconfined quantum critical point, highlighting observable features in spectral functions.

Contribution

It provides the first detailed dynamical spectral analysis of a deconfined quantum critical point with emergent O(4) symmetry, linking theoretical predictions with potential experimental detection.

Findings

Broad continua in spin structure factors indicate fractionalized excitations.

Distinct spectral features such as the continuum edge are identified.

Comparison with Landau transition shows unique signatures of fractionalization.

Abstract

Deconfined quantum critical points govern continuous quantum phase transitions at which fractionalized (deconfined) degrees of freedom emerge. Here we study dynamical signatures of the fractionalized excitations in a quantum magnet (the easy-plane J-Q model) that realize a deconfined quantum critical point with emergent O(4) symmetry. By means of large-scale quantum Monte Carlo simulations and stochastic analytic continuation of imaginary-time correlation functions, we obtain the dynamic spin structure factors in the $S^{x}$ and $S^{z}$ channels. In both channels, we observe broad continua that originate from the deconfined excitations. We further identify several distinct spectral features of the deconfined quantum critical point, including the lower edge of the continuum and its form factor on moving through the Brillouin Zone. We provide field-theoretical and lattice model calculations that explain the overall shapes of the computed spectra, which highlight the importance of interactions and gauge fluctuations to explaining the spectral-weight distribution. We make further comparisons with the conventional Landau O(2) transition in a different quantum magnet, at which no signatures of fractionalization are observed. The distinctive spectral signatures of the deconfined quantum critical point suggest the feasibility of its experimental detection in neutron scattering and nuclear magnetic resonance experiments.