SKM 2023 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 12: Topological Insulators (joint session MA/TT)

TT 12.7: Vortrag

Montag, 27. März 2023, 16:45–17:00, HSZ 403

Thermal Hall Effect of Magnon-Phonon Hybrid Quasiparticles in a Fluctuating Heisenberg-Kitaev Antiferromagnet — •Robin R. Neumann¹, Alexander Mook², Jürgen Henk¹, and Ingrid Mertig¹ — ¹Martin Luther University Halle-Wittenberg, Halle (Saale), Germany — ²Johannes Gutenberg University, Mainz, Germany

Magnons, the quantized excitations of localized spins, and phonons, the quantized excitations of the lattice, are two types of quasiparticles that are responsible for heat transport in magnetic insulators. However, phonons by themselves do not contribute to the transverse heat current induced by a temperature gradient, i.e., the thermal Hall effect (THE). Magnons, on the other hand, may exhibit a Berry curvature, a magnetic field in reciprocal space, that leads to an intrinsic THE.

In this talk, I address the THE in a Heisenberg-Kitaev antiferromagnet subjected to a magnetic field. The applied field drives the system from a zigzag antiferromagnetic to a spin-flop state. The magnon-driven THE indicates the magnetic phase transition by a sign change at the critical field. Furthermore, when the magnetoelastic interaction is considered, the phonon and magnon bands hybridize and additional Berry curvature at the avoided crossings emerge. Depending on the strength of the spin-phonon coupling, this may lead to an overall reversal of the THE while the field-induced sign change at the critical field remains mostly robust. These results showcase that magnon-phonon hybridization can be pivotal for the interpretation of transport experiments.