Fractional Spin Fluctuation as a Precursor of Quantum Spin Liquids: Majorana Dynamical Mean-Field Study for the Kitaev Model

TL;DR

This study demonstrates that precursor signs of quantum spin liquids can be detected in spin dynamics at higher temperatures using advanced theoretical methods on the Kitaev model.

Contribution

The paper introduces a novel theoretical approach combining cluster dynamical mean-field theory and quantum Monte Carlo in the Majorana fermion framework to study spin dynamics.

Findings

Dynamical spin correlations exhibit unique temperature and frequency dependence.

Precursor signs of quantum spin liquids appear in spin dynamics well above the ground state.

Results suggest experimentally accessible indicators of fractionalized spins.

Abstract

Experimental identification of quantum spin liquids remains a challenge, as the pristine nature is to be seen in asymptotically low temperatures. We here theoretically show that the precursor of quantum spin liquids appears in the spin dynamics in the paramagnetic state over a wide temperature range. Using the cluster dynamical mean-field theory and the continuous-time quantum Monte Carlo method, which are newly developed in the Majorana fermion representation, we calculate the dynamical spin structure factor, relaxation rate in nuclear magnetic resonance, and magnetic susceptibility for the honeycomb Kitaev model whose ground state is a canonical example of the quantum spin liquid. We find that dynamical spin correlations show peculiar temperature and frequency dependence even below the temperature where static correlations saturate. The results provide the experimentally-accessible symptoms of the fluctuating fractionalized spins evincing the quantum spin liquids.