Transport and spectroscopic signatures of a disorder-stabilized metal in two-dimensional frustrated Mott insulators

TL;DR

This study uses nonperturbative numerical methods to explore how disorder induces an insulator-metal transition in a two-dimensional frustrated Mott insulator, revealing an antiferromagnetic metal phase with unique quantum critical behavior.

Contribution

First nonperturbative numerical investigation of disorder-induced insulator-metal transition in 2D frustrated Mott insulators, with comparison to experimental Cu-intercalated 1T-TaS2 data.

Findings

Identification of an antiferromagnetic metal phase under moderate disorder.

Discovery of two quantum critical points unrelated to magnetic correlation loss.

Observation of a resilient non-Fermi liquid metallic state.

Abstract

Frustrated Mott insulators such as transition metal dichalcogenides present an ideal platform for the experimental realization of externally tuned insulator-metal transition. In this paper, we present the first nonperturbative numerical investigation of the disorder-induced insulator-metal transition in a two-dimensional frustrated Mott insulator. Our approach is generic and captures the essential physics of Mott insulator-metal transition in geometrically frustrated lattices. For concreteness, we have compared our results with the experimental observations on copper (Cu) intercalated 1T-TaS2. Based on the magnetic, spectroscopic, and transport signatures, we have mapped out the thermal phase diagram of Cu intercalated 1T-TaS2 and established that over a regime of moderate disorder strength this material hosts an antiferromagnetic metal. Moreover, the insulator-metal transition in this system is not tied to the loss of magnetic correlations, thereby giving rise to two quantum critical points. The emergent non-Fermi liquid metal is governed by resilient quasiparticles, that survive as the relevant low energy excitations even after the break down of the Fermi liquid description. The transport and spectroscopic signatures discussed in this paper are expected to serve as important benchmarks for future experiments on this and related class of materials.