Optical spin-caloritronic effects of exciton-polaritons

We establish a kinetic framework for optical spin-caloritronic transport in exciton-polariton microcavities. We show that a neutral, incoherent polariton gas converts heat flow into particle and pseudospin currents whose directions are dictated by the topology of the spin-orbit interaction (SOI) induced effective field, while their magnitudes reflect the local imbalance between high- and low-momentum populations. Treating the momentum-dependent SOI as the key geometric constraint, we analyze the propagation of polaritons shaped by the intrinsic TE-TM polarization splitting and by the Zeeman splitting induced by an externally applied out-of-plane magnetic field, all within a smoothly varying temperature landscape. We identify four distinct optical analogues of thermoelectric effects. A thermal gradient alone drives the flow of radial density, resulting in the optical Seebeck effect. Adding a Zeeman field yields an optical spin Seebeck effect manifested by circular-polarization flows. The replacement of the Zeeman field with the TE-TM splitting deflects the pseudo-spin azimuthally, producing an optical spin Nernst effect. When both splittings act simultaneously, a longitudinal spin Nernst current emerges. This taxonomy of spin-caloritronic regimes links each effect to a symmetry of the effective field and provides design rules for heat-to-spin conversion in hybrid light-matter systems.