High-pressure X-ray diffraction study of 1T-TaS2

Abstract

We present a room temperature high-pressure X-ray diffraction study of the layered compound 1T-TaS2 up to 20GPa. This material is known to exhibit a variety of structural phase transitions that are ascribed to the stabilization of charge density wave states. It has been recently shown that at pressures larger than 3GPa and up to 25GPa, 1T-TaS2 becomes superconductor below about 5K. It was suggested that this superconductivity coexists with different CDW states, an hypothesis that can be tested by X-ray diffraction. Our first results at room temperature show that at around 1.9GPa, the nearly-commensurate (NCCDW) phase transforms into a phase similar to the high temperature incommensurate phase (ICCDW). Above 9GPa, we show the existence of another IC phase, still discernable up to 20GPa despite the pressure-induced crystal damage above 13GPa. These results are consistent with resistivity measurements, but call for a complete exploration of the P–T phase diagram of 1T-TaS2.