Transport evidence for the orbital Nernst effect.

Orbital Hall effects have recently attracted significant attention for generating substantial orbital angular momentum currents in both strong- and weak-spin-orbit-coupling materials. Despite extensive theoretical and experimental progress on the orbital Hall effect, its thermal counterpart, in which a temperature gradient drives a transverse orbital current, known as the orbital Nernst effect, has remained experimentally elusive. Here, we report the first experimental evidence for the orbital Nernst effect by measuring the magneto-thermopower in the yttrium iron garnet (YIG)/Pt/CuOx heterostructures. Through systematic comparison with the YIG/Pt and YIG/CuOx heterostructures, we show that both the magneto-thermopower and the magnetoresistance for YIG/Pt/CuOx are markedly enhanced due to the contributions from the orbital Nernst effect and the orbital Hall effect in CuOx, respectively. Our experimental evidence for the orbital Nernst effect supports the orbital degree of freedom as a promising route for heat-energy harvesting and orbital angular momentum thermal transport in earth-abundant materials.