Disorder unveils Mott quantum criticality behind a first-order transition in the quasi-two-dimensional organic conductor κ−(ET)2Cu[N(CN)2]Cl

Abstract

We show the significant impact of weak disorder on the Mott transition by investigating electronic transport in a systematically x-ray-irradiated layered organic conductor under continuous pressure control. The critical end point of the first-order Mott transition is dramatically suppressed by such weak disorder that causes only a minor reduction in the transition temperature of disorder-sensitive nodal superconductivity. Instead, quantum critical scaling of resistance holds at lower temperatures and Fermi-liquid coherence temperature on the metallic side is lowered. Introducing disorder unveils the interaction-induced quantum criticality hidden behind the first-order transition.