Spinon Fractionalization from Dynamic Structure Factor of Spin-1/2 Heisenberg Antiferromagnet on the Kagome Lattice

TL;DR

This paper investigates the dynamical spin structure factor of the spin-1/2 Heisenberg antiferromagnet on the kagome lattice, revealing spinon fractionalization and its sensitivity to interactions, consistent with experimental neutron scattering data.

Contribution

It provides a detailed analysis of the dynamical response and spinon excitations in the kagome antiferromagnet, highlighting the effects of Dzyaloshinskii-Moriya interactions and identifying the quantum phase transition mechanism.

Findings

Spectral intensity peaks at low frequency near Q = M point

Broad spectral distribution at high frequency along Brillouin zone boundary

Identification of critical spinon excitation spectrum

Abstract

We study dynamical spin structure factor (DSSF) of S = 1/2 Heisenberg model on the kagome lattice (KAFM) by means of density-matrix renormalization group. By comparison with the well-defined magnetic ordered state and chiral spin liquid sitting nearby in the phase diagram, the KAFM with the nearest-neighbor interaction shows distinct dynamical response behaviors. First of all, the DSSF displays important spectral intensity predominantly at low frequency region around Q = M point in momentum space, and shows a broad spectral distribution at high frequency region for momenta along the boundary of the extended Brillouin zone. Secondly, spinon excitation spectrum is identified from momentum and energy resolved DSSF, which shows critical behavior with much reduced spectrum intensity comparing to the neighboring chiral spin liquid. By adding a weak Dzyaloshinkii-Moriya interaction, the DSSF demonstrates a strong sensitivity to the boundary condition smore consistent with a gapless spin liquid. These results capture the main observations in the inelastic neutron scattering measurements of herbertsmithite, and indicate the spin liquid nature of the ground state with fractionalized spinon excitations. By following the DSSF crossing the quantum phase transition between the CSL and the magnetical ordered phase, we identify the spinon condensation driving the quantum phase transition.