Pressure-induced insulator to metal transition of mixed valence compound Ce(O,F)SbS2

Abstract

Transport properties of CeO0.85F0.15SbS2 and undoped CeOSbS2 under high pressure were investigated experimentally and theoretically. Electrical resistivity measurements of the CeO0.85F0.15SbS2 single crystals were performed under various high pressures using a diamond anvil cell with boron-doped diamond electrodes. The samples showed the insulator to metal transition by applying a high pressure up to 30-40 GPa. On the other hand, the undoped CeOSbS2 showed almost the same transport property with the F-doped sample under high pressure. The valence state analysis using X-ray photoelectron spectroscopy revealed a simple valence state of Ce3+ in CeO0.85F0.15SbS2 and mixed valence state between Ce3+ and Ce4+ in undoped CeOSbS2. The valence fluctuation in Ce carried out the comparable transport nature in both samples. A band calculation suggests that the undoped CeOSbS2 could be metallic under high pressure of 30 GPa in accordance with the experimental results. A superior thermoelectric property of power factor in CeOSbS2 was estimated under high pressure around 20 GPa in comparison with that of ambient pressure.