Thermal Hall effects due to topological spin fluctuations in YMnO${}_3$

Abstract

The thermal Hall effect in magnetic insulators has been considered a powerful method for examining the topological nature of charge-neutral quasiparticles such as magnons. Yet, unlike the kagome system, the triangular lattice has received less attention for studying the thermal Hall effect because the scalar spin chirality cancels out between adjacent triangles. However, such cancellation cannot be perfect if the triangular lattice is distorted, which could open the possibility of a non-zero thermal Hall effect. Here, we report that the trimerized triangular lattice of multiferroic hexagonal manganite YMnO${}_3$ produces a highly unusual thermal Hall effect due to topological spin fluctuations with the additional intricacy of a Dzyaloshinskii-Moriya interaction under an applied magnetic field. We conclude the thermal Hall conductivity arises from the system's topological nature of spin fluctuations. Our theoretical calculations demonstrate that the thermal Hall conductivity is also related in this material to the splitting of the otherwise degenerate two chiralities, left and right, of its 120${}^{\circ }$ magnetic structure. Our result is one of the most unusual cases of topological physics due to this broken $Z_2$ symmetry of the chirality in the supposedly paramagnetic state of YMnO${}_3$, with strong topological spin fluctuations. These new mechanisms in this important class of materials are crucial in exploring new thermal Hall physics and exotic excitations.

14 pages, 3 figures; accepted for publication in Nature Communications

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Cited by in corpus (10)

• Thermal Hall effects in quantum magnets
• Phonon thermal Hall effect in Mott insulators via skew-scattering by the scalar spin chirality
• Thermal Hall Effect of Magnons from Many-Body Skew Scattering
• Exchange striction induced thermal Hall effect in van der Waals antiferromagnet MnPS${}_3$
• Phonon thermal Hall effect in non-magnetic Y${}_2$Ti${}_2$O${}_7$
• Frustration and chirality in three-dimensional trillium lattices: Insights and Perspectives
• High-throughput search for topological magnon materials
• Magnetoelectric coupling and its impact on the multicaloric effect
• Spin-phonon coupling and thermal Hall effect in the Kitaev model
• Classification of magnon thermal Hall systems based on U(1) to non-Abelian gauge fields