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Understanding Anomalous Magnetothermal Transport via Disentangling Shear and Compression Phonons

Magnetothermal transport in various frustrated magnets exhibits striking field-dependent anomalies that deviate from conventional magnon or phonon transport. To understand such anomalies, this work derives an effective spin–phonon Hamiltonian in which phonons with different polarizations couple selectively to distinct spin operators in the strong spin–orbit coupling limit.
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Publication Date: July 8, 2026

Authors: Haoting Xu, Antoine Matar, Hae-Young Kee

Abstract:

Magnetothermal transport in various frustrated magnets exhibits striking field-dependent anomalies that deviate from conventional magnon or phonon transport. To understand such anomalies, we derive an effective spin-phonon Hamiltonian in which phonons with different polarizations couple selectively to distinct spin operators in the strong spin-orbit coupling limit, and show that symmetry-constrained spin-lattice coupling naturally leads to mode-selective spin-phonon interactions. As a result, compression and shear phonon modes contribute to spin heat current across different magnetic-field regimes. Using a Landauer transport framework combined with exact diagonalization of spin chains coupled to a phonon bath, we show that this mechanism produces a characteristic peak-dip-peak structure in the field dependence of heat current, providing a microscopic explanation for field-induced transport anomalies in spin-orbit-coupled Mott insulators.

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