Spin-phonon hybridization and its direct effect on thermal transport in the frustrated triangular magnet CsYbSe₂.

The thermal conductivity of CsYbSe₂, and in fact many other frustrated magnets, often exhibits strong, non-monotonic field-dependence, even when the state of magnetic lattice is disordered and a coherenet itinerant magnetic contribution is absent. We present a novel and highly-generic way in which phonon heat conduction can acquire unique nontrivial field-dependence through the hybridization of acoustic phonons and spin flip excitations via strain-modulation of the magnetic g-tensor. Analytical modelling of the hybridized spectra of this model under applied fields is successful in reproducing the qualitative features of transport data in CsYbSe₂, and is potentially widely applicable to many other insulating magnetic systems.