Antisymmetric versus anisotropic exchange: shaping topological excitation spectra and transport properties of Heisenberg-Kitaev magnets*

Ever since their conception, Kitaev interactions have been a continuous source of exotic topological topological effects in the field of quantum magnetism. This concerns not only the ground state properties of Kitaev materials which potentially host Majorana fermions, but also their magnonic excitation spectra. In honeycomb Heisenberg-Kitaev magnets, the anisotropic bond-directional exchange interactions can lead to the emergence of a topological magnon-insulator, characterized by a nontrivial first Chern number. The magnon spectrum bears witness to the underlying magnetic interactions, and can in principle be used to quantify the relevance of anisotropic exchange experimentally by the means of ineleastic neutron scattering. Spin-orbit coupling, which is the major driving force behind those interactions, can however lead to other magnetic interactions such as the Dzyaloshinskii-Moriya interaction (DMI) which might interfere in this procedure [1]. By referring to linear spin wave theory, we study the honeycomb Heisenberg-Kitaev model in the presence of DMI in order to understand the competition between the spin-orbit driven DMI and Kitaev interaction and its impact on the magnon spectrum and thermal transport properties [2]. Based on our results, we propose a strategy to disentangle the two types of interactions experimentally and explore magnon-induced electronic orbital magnetism as a new channel which can reveal the complexity of magnetic interactions [3].

[1] Zhu et al., Sci Adv. 7, eabi7532 (2021)

[2] Zhang et al. PRB 103, 134414 (2021)

[3] Zhang et al. Commun. Phys. 3, 227 (2020)