Title: Separation of the charge density wave and superconducting states by an intermediate semimetal phase in pressurized TaTe2,
Abstract: In layered transition metal dichalcogenides (LTMDCs) that display both charge
density waves (CDWs) and superconductivity, the superconducting state generally
emerges directly on suppression of the CDW state. Here, however, we report a
different observation for pressurized TaTe2, a non-superconducting CDW-bearing
LTMDC at ambient pressure. We find that a superconducting state does not occur
in TaTe2 after the full suppression of its CDW state, which we observe at about
3 GPa, but, rather, a non-superconducting semimetal state is observed. At a
higher pressure, ~21 GPa, where both the semimetal state and the corresponding
positive magnetoresistance effect are destroyed, superconductivity finally
emerges and remains present up to ~50 GPa, the high pressure limit of our
measurements. Our pressure-temperature phase diagram for TaTe2 demonstrates
that the CDW and the superconducting phases in TaTe2 do not directly transform
one to the other, but rather are separated by a semimetal state, - the first
experimental case where the CDW and superconducting states are separated by an
intermediate phase in LTMDC systems.