Radiative spin caloritronics in nonreciprocal many-body systems
The authors predict a spin thermal Hall effect (STHE) in nonreciprocal magneto-optical systems where a longitudinal heat current creates a transverse accumulation of photon spin angular momentum. This STHE is the Onsager-Casimir reciprocal counterpart to the inverse spin thermal Hall effect, establishing a unified thermodynamic framework for photon spin caloritronics and identifying 'photon spin' as a genuine transport variable.