Colossal Density-Driven Resistance Response in the Negative Charge Transfer Insulator MnS2

A reversible density driven insulator to metal to insulator transition in high-spin MnS2 is experimentally observed, leading with a colossal electrical resistance drop of 10(8) Omega by 12 GPa. Density functional theory simulations reveal the metallization to be unexpectedly driven by previously unoccupied S-2(-2) sigma*(3p) antibonding states crossing the Fermi level. This is a unique variant of the charge transfer insulator to metal transition for negative charge transfer insulators having anions with an unsaturated valence. By 36 GPa the emergence of the low-spin insulating arsenopyrite (P2(1)/c) is confirmed, and the bulk metallicity is broken with the system returning to an insulative electronic state.