Pressure‐Induced Re‐Entrant Superconductivity in Transition Metal Dichalcogenide TiSe2

Abstract

AbstractTransition metal dichalcogenide TiSe2 exhibits a superconducting dome within a low pressure range of 2–4 GPa, which peaks with the maximal transition temperature Tc of ≈1.8 K. Here it is reported that applying high pressure induces a new superconducting state in TiSe2, which starts at ≈16 GPa with a substantially higher Tc that reaches 5.6 K at ≈21.5 GPa with no sign of decline. Combining high‐throughput first‐principles structure search, X‐ray diffraction, and Raman spectroscopy measurements up to 30 GPa, It is found that TiSe2 undergoes a first‐order structural transition from the 1T phase under ambient pressure to a new 4O phase under high pressure. Comparative ab initio calculations reveal that while the conventional phonon‐mediated pairing mechanism may account for the superconductivity observed in 1T‐TiSe2 under low pressure, the electron‐phonon coupling of 4O‐TiSe2 is too weak to induce a superconducting state whose transition temperature is as high as 5.6 K under high pressure. The new superconducting state found in pressurized TiSe2 requires further study on its underlying mechanism.