Angular-dependent thermal Hall effect in a honeycomb magnet: Disentangling Kitaev and Dzyaloshinskii-Moriya interactions

Layered honeycomb magnets have garnered significant attention recently for their exotic quantum phenomena due to the potential anisotropic, bond-dependent Kitaev interactions. However, distinguishing the roles of Kitaev interactions and the symmetry-allowed Dzyaloshinskii-Moriya interaction (DMI) remains challenging, since both mechanisms may lead to similar magnetic excitations and thermal transport properties. To tackle this challenge, using a ferromagnetic honeycomb insulator VI3 as a model system, we systematically study the angular-dependent thermal Hall conductivity Kxy(θ, Φ) with both out-of-plane (θ) and in-plane (Φ) magnetic field rotations. Our results reveal a persistent thermal Hall response for both out-of-plane and in-plane rotating magnetic fields, devoid of the sign-reversal patterns characteristic of Kitaev physics. Instead, quantitative analysis shows that the angular dependent Kxy(θ, Φ) is governed by the projection between the magnetic moment and a tilted DM vector containing both out-of-plane and in-plane components. These results not only establish the DMI-driven topological magnetic excitations as the origin of the thermal Hall response in VI3 but also highlight the angular-dependent thermal Hall effect measurements as an effective approach for distinguishing competing interactions in quantum magnets.