Origin of the anomalous thermal Hall effect in ferromagnets

Determine whether magnons or phonons are the primary microscopic origin of the anomalous thermal Hall effect observed in ferromagnetic materials that exhibit spontaneous time-reversal-symmetry breaking.

Background

The thermal Hall effect has been observed across many insulating systems. In ferromagnets, an anomalous thermal Hall response indicative of spontaneous time-reversal-symmetry breaking has been reported, but the microscopic mechanism producing this effect is debated.

Clarifying whether magnons or phonons dominate the anomalous thermal Hall effect is essential for understanding heat-carrying quasiparticles and the role of Berry curvature and spin–lattice coupling in ferromagnets. The present work highlights related phenomena in altermagnets and motivates settling this question.