Pressure-induced metallic state in a van der Waals cluster Mott insulator Nb3Cl8

We report on the pressure-induced metallization of a van der Waals cluster Mott insulator Nb3Cl8 by employing the resistivity measurements under high pressure. Upon compression, its resistance and energy gap are suppressed gradually with exhibiting the fully metallic state at a critical pressure of Pc ≈ 70 GPa. Hall resistance measurements revealed a significant band-structure reconstruction around Pc, where the dominant charge carriers are altered from hole-to electron-type and the carrier concentration experiences a sharp increase in the metallic state. In addition, high-pressure synchrotron XRD measurements uncover a possible structural phase transition around Pc. Our further first-principles calculations reproduced the pressure-driven structure transition and the corresponding metallic state above Pc. The present study demonstrates a feasible high-pressure route to realize the metallization of cluster Mott insulator Nb3Cl8.