Unveiling the pressure-driven metal–semiconductor–metal transition in the doped TiS₂

Conventional theories expect that materials under pressure exhibit expanded valence and conduction bands, leading to increased electrical conductivity. Here, we report the electrical properties of the doped 1T-TiS₂ under high pressure by electrical resistance investigations, synchrotron x-ray diffraction, Raman scattering and theoretical calculations. Up to 70 GPa, an unusual metal–semiconductor–metal transition occurs. Our first-principles calculations suggest that the observed anti-Wilson transition from metal to semiconductor at 17 GPa is due to the electron localization induced by the intercalated Ti atoms. This electron localization is attributed to the strengthened coupling between the doped Ti atoms and S atoms, and the Anderson localization arising from the disordered intercalation. At pressures exceeding 30.5 GPa, the doped TiS₂ undergoes a re-metallization transition initiated by a crystal structure phase transition. We assign the most probable space group as P2₁2₁2₁. Our findings suggest that materials probably will eventually undergo the Wilson transition when subjected to sufficient pressure.