Understanding Anomalous Magnetothermal Transport via Disentangling Shear and Compression Phonons

TL;DR

This paper develops a microscopic model explaining anomalous magnetothermal transport in frustrated magnets by mode-selective spin-phonon interactions, revealing how different phonon modes contribute to heat transport under magnetic fields.

Contribution

It introduces an effective spin-phonon Hamiltonian with symmetry-constrained mode selectivity, explaining field-dependent transport anomalies in spin-orbit-coupled Mott insulators.

Findings

Mode-selective spin-phonon coupling leads to distinct contributions of compression and shear phonons.

The model reproduces a peak-dip-peak structure in heat current versus magnetic field.

Microscopic explanation for field-induced transport anomalies in frustrated magnets.

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.