Observation of three superconducting transitions in the pressurized CDW-bearing compound TaTe2

Transition metal dichalcogenides host a wide variety of lattice and\nelectronic structures, as well as corresponding exotic physical properties,\nespecially under certain tuning conditions. Here, we are the first to report\nthe observation of pressure-induced three superconducting transitions in TaTe2,\na charge density wave (CDW) - bearing layered transition-metal dichalcogenide\nthat is metallic but not superconducting at ambient pressure. We find that its\nCDW state can be easily suppressed upon increasing pressure up to ~ 1 GPa. A\nsuperconducting state then emerges from the suppressed CDW state and persists\nto the pressure about 7 GPa. Unexpectedly, another superconducting state\nappears at ~ 11 GPa within the same monoclinic (M) structure of its\nambient-pressure one. Upon further compression to 21 GPa, a third\nsuperconducting state with higher Tc appears from a high-pressure (HP) phase.\nOur experimental results suggest that the pressure-induced three\nsuperconducting transitions in TaTe2 are respectively driven by the suppression\nof the CDW state, the change of the angle in the M phase and the transition of\nM-to-HP phase. These results demonstrate not only the versatile nature of this\ncorrelated electron system, but also the first experimental example that shows\nthe pressure-induced evolution from a CDW state to three superconducting states\ndriven by different mechanisms.\n