We introduce a matrix-product state based method to efficiently obtain dynamical response functions for two-dimensional microscopic Hamiltonians, which we apply to different phases of the Kitaev-Heisenberg model. We find significant broad high energy features beyond spin-wave theory even in the ordered phases proximate to spin liquids. This includes the phase with zig-zag order of the type observed in α-RuCl3, where we find high energy features like those seen in inelastic neutron scattering experiments. Our results provide an example of a natural path for proximate spin liquid features to arise at high energies above a conventionally ordered state, as the diffuse remnants of spin-wave bands intersect to yield a broad peak at the Brillouin zone center.
@article{arxiv.1701.04678,
title = {Dynamics of the Kitaev-Heisenberg Model},
author = {Matthias Gohlke and Ruben Verresen and Roderich Moessner and Frank Pollmann},
journal= {arXiv preprint arXiv:1701.04678},
year = {2017}
}