Evolution of structural and electronic properties of TiSe2 under high pressure

A pressure-induced structural phase transition and its intimate link with the superconducting transition was studied for the first time in TiSe2 up to 40 GPa at room temperature using X-ray diffraction, transport measurement, and first-principles calculations. We demonstrate the occurrence of a first-order structural phase transition at 4 GPa from the standard trigonal structure (S.G.P3¯m1) to another trigonal structure (S-G-P3¯c1). Additionally, at 16 GPa, the P3¯c1 phase spontaneously transforms into a monoclinic C2/m phase, and above 24 GPa, the C2/m phase returns to the initial P3¯m1 phase. Electrical transport results show that metallization occurs above 6 GPa. The charge density wave …