title: Fractional Spin Fluctuations as a Precursor of Quantum Spin Liquids: Majorana Dynamical Mean-Field Study for the Kitaev Model.
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.
authors: Department of Applied Physics, University of Tokyo, Bunkyo, Tokyo 113-8656, Japan.
authors: Junki
authors: J
authors: Yoshitake
authors: Department of Physics, Tokyo Institute of Technology, Meguro, Tokyo 152-8551, Japan.
authors: Joji
authors: J
authors: Nasu
authors: Department of Applied Physics, University of Tokyo, Bunkyo, Tokyo 113-8656, Japan.
authors: Yukitoshi
authors: Y
authors: Motome