Low temperature thermopower in CoSbS

Thermopower of FeSb2 reaches colossal values of up to -45 mV/K, however, the physical mechanism is not well understood. In order to make progress and enable predictive materials design, it is important to discover new materials with high thermoelectric parameters and with tunable physical properties. Recently, it was shown that CoSbS could be a high-temperature thermoelectric material due to several positive factors that work simultaneously to enhance its thermoelectric performance. We report giant thermopower S = 2.5 mV/K in CoSbS single crystals [1], a material that shows strong high-temperature thermoelectric performance when doped with Ni or Se. Changes of low temperature thermopower induced by magnetic field point to mechanism of electronic diffusion of carriers in the heavy valence band. Intrinsic magnetic susceptibility is consistent with the Kondo-Insulator-like accumulation of electronic states around the gap edges. This suggests that giant thermopower stems from temperature-dependent renormalization of the noninteracting bands and buildup of the electronic correlations on cooling.
[1]. Q Du, M Abeykoon, Y Liu, G Kotliar, C Petrovic, Physical review letters 123 (7), 076602.