# Dynamics of the Kitaev-Heisenberg Model

## TL;DR

This paper presents a matrix-product state method to compute dynamical responses in the Kitaev-Heisenberg model, revealing high-energy features related to spin liquids that align with experimental observations.

## Contribution

Introduces a novel matrix-product state approach for dynamical functions in 2D Hamiltonians, applied to the Kitaev-Heisenberg model, uncovering high-energy spin liquid signatures.

## Key findings

- High energy features beyond spin-wave theory in ordered phases
- Observation of experimental-like features in zig-zag ordered phase
- Proximity of spin liquid features at high energies

## Abstract

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 $\alpha$-RuCl$_3$, 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.