Emergence of a Novel Pseudogap Metallic State in a Disordered 2D Mott Insulator

Abstract

We explore the nature of the phases and an unexpected disorder-driven Mott insulator to metal transition in a single crystal of the layered dichalcogenide $1\mathrm{T}\text{\ensuremath{-}}{\mathrm{TaS}}_{2}$ that is disordered without changing the carrier concentration by Cu intercalation. Angle resolved photoemission spectroscopy measurements reveal that increasing disorder introduces delocalized states within the Mott gap that lead to a finite conductivity, challenging conventional wisdom. Our results not only provide the first experimental realization of a disorder-induced metallic state but in addition also reveal that the metal is a non-Fermi liquid with a pseudogap with a suppressed density of states that persists at finite temperatures. Detailed theoretical analysis of the two-dimensional disordered Hubbard model shows that the novel metal is generated by the interplay of strong interaction and disorder.