Thermoelectric Power Investigation on SmS

We construct a measurement system of the absolute thermoelectric power, and present experimental results of the Seebeck coefficient S (T, P) of samarium mono-sulphide (SmS) at ambient and high pressure. At ambient pressure, S (T) of SmS exhibits negative sign and its absolute value vertical bar S vertical bar steeply increases with lowering temperature, indicating that the dominant charge carrier is an electron and the energy gap opens at Fermi level. When increasing pressure at room temperature, S (P) sharply changes from a negative to positive value at the black-to-golden phase transition, indicating that the dominant carrier changes from electrons to holes possibly associated with the discontinuous collapse of the band gap at the transition.