Pressure-induced bulk superconductivity in a layered transition-metal dichalcogenide 1T -tantalum selenium

We report pressure-driven superconductivity (SC) in the vicinity of a commensurate charge-density wave (CCDW) in transition-metal dichalcogenides (TMDs) 1T-TaSe2 by simultaneous resistivity and ac susceptibility. The superconducting phase enters at 4.5 GPa and bulk SC emerges along with the collapse of the CCDW phase at a critical pressure Pc∼6.5GPa. Higher than Pc, the superconducting transition temperature (Tc) keeps increasing linearly, without a dome-shaped superconducting diagram in our pressure range. Tc reaches ∼5.3K at 15 GPa, which is the highest among all 1T-TMDs. A comprehensive analysis shows that electronic correlations of the CCDW phase open energy gaps, which prohibit Cooper pairing, while the superconducting channels and CCDW domain wall coexist in three dimensions above Pc. The evolutions of the Fermi surface and the softening of phonon modes under pressure are proposed to explain the monotonic increase of Tc. The findings reveal the interplay of CCDW and SC in 1T-TaSe2 by a clean method, viz., high pressure, and shed light on the underlying superconducting mechanism in the relevant systems.