Pressure induced semimetal-to-metal transition and new structure of TaNiSeabove 10 GPa.

Previous studies of the transition metal chalcogenide TaNiSehas identified two phase transitions occurring between 0-10 GPa, involving the excitonic insulator-to-semiconductor transition at 1 GPa and the semiconductor-to-semimetal transition at 3 GPa. However, there is still a lack of in-depth research on the changes in its physical properties changes above 10 GPa. In this study, TaNiSewere investigated under high-pressure conditions using high-pressure x-ray diffraction and high-pressure x-ray absorption experiments. During the experimental process, a novel phase transition from the semimetal to the metal phase was observed between 10-60 GPa, specifically between 10-14 GPa, and the structure of the new phase was determined to be P2/m through first-principles calculations. This transition mechanism is attributed to the sliding of the weakly coupled layers of TaNiSewithin theplane, leading to changes in the crystal lattice constants and symmetry. This research fills a gap in the understanding of TaNiSe's crystal structure under high pressure and contributes to the broader field of transition metal chalcogenides.