Pressure-induced evolution of structural and electronic properties in TiTe2

Bulk 1T-TiTe2 (hexagonal, space group P-3m1) exhibits semimetallic conductivity with weak Anderson localization characteristic at ambient pressure, but superconductivity under high pressure of similar to 5GPa. Here the detailed evolutions of structural and transport properties in TiTe2 during compression are investigated by extending pressure up to 50.2 GPa. The combined high-pressure electrical transport and synchrotron x-ray diffraction experiments unravel two critical pressure points. At P-c1 similar to 5.4GPa, the superconductivity emerges, which is accompanied by a structural transition from P-3m1 to a mixture of P-3m1 and monoclinic C2/m phase. The localization effect maintains until the structural transition is over at P-c2 similar to 19.1GPa, meanwhile the Hall coefficient RH changes from positive to negative. Our results demonstrate that the superconductivity in the pressurized TiTe2 can be assigned to the high-pressure C-2/m phase which is electron dominated.