title: Low-Energy Spin Dynamics of the Honeycomb Spin Liquid Beyond the Kitaev Limit.
abstract: We investigate the generic features of the low energy dynamical spin structure factor of the Kitaev honeycomb quantum spin liquid perturbed away from its exact soluble limit by generic symmetry-allowed exchange couplings. We find that the spin gap persists in the Kitaev-Heisenberg model, but generally vanishes provided more generic symmetry-allowed interactions exist. We formulate the generic expansion of the spin operator in terms of fractionalized Majorana fermion operators according to the symmetry enriched topological order of the Kitaev spin liquid, described by its projective symmetry group. The dynamical spin structure factor displays power-law scaling bounded by Dirac cones in the vicinity of the Γ, K, and K^{'} points of the Brillouin zone, rather than the spin gap found for the exactly soluble point.
authors.affiliation: International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China.
authors.forename: Xue-Yang
authors.initials: XY
authors.lastname: Song
authors.affiliation: Department of Physics, University of California, Santa Barbara, California 93106, USA.
authors.forename: Yi-Zhuang
authors.initials: YZ
authors.lastname: You
authors.affiliation: Kavli Institute of Theoretical Physics, University of California, Santa Barbara, California 93106, USA.
authors.forename: Leon
authors.initials: L
authors.lastname: Balents