Pressure-induced superconductivity in semimetallic 1T-TiTe2 and its persistence upon decompression

Pristine 1T-TiTe2 single crystal has been studied for resistance and magnetoresistance behavior under quasihydrostatic and nonhydrostatic compressions. While the semimetallic state is retained in nearly hydrostatic pressures, small nonhydrostatic compression leads to an abrupt change in low-temperature resistance, a signature of possible charge density wave (CDW) ordering, that eventually collapses above 6.2 GPa. Superconductivity emerges at similar to 5 GPa, rapidly increasing to a critical temperature (T-c) of 5.3 K at 12 GPa, irrespective of pressure condition. Pressure studies thus evidence that 1T-TiTe2 exhibits superconductivity irrespective of the formation of the CDW-like state, implying the existence of phase-separated domains. Most surprisingly, the superconducting state persists upon decompression, establishing a novel phase diagram with suppressed P scale. The pressure quenchable superconductivity, of multiband nature and relatively high upper critical field, makes 1T-TiTe2 unique among other layered dichalcogenides.