A Microscopic View on the Mott transition in Chromium-doped V2O3

TL;DR

This paper uses microscopic imaging to reveal how the metal-insulator transition in chromium-doped V2O3 occurs through phase separation at submicron scales, advancing understanding of Mott transitions.

Contribution

First microscopic observation of phase separation during the Mott transition in Cr-doped V2O3 with submicron resolution.

Findings

Microscopic metallic domains coexist with insulating background during transition

Phase separation explains the poor metallicity of the paramagnetic metal phase

Pressure suppresses phase separation, leading to a homogeneous metallic state

Abstract

V2O3 is the prototype system for the Mott transition, one of the most fundamental phenomena of electronic correlation. Temperature, doping or pressure induce a metal to insulator transition (MIT) between a paramagnetic metal (PM) and a paramagnetic insulator (PI). This or related MITs have a high technological potential, among others for intelligent windows and field effect transistors. However the spatial scale on which such transitions develop is not known in spite of their importance for research and applications. Here we unveil for the first time the MIT in Cr-doped V2O3 with submicron lateral resolution: with decreasing temperature, microscopic domains become metallic and coexist with an insulating background. This explains why the associated PM phase is actually a poor metal. The phase separation can be associated with a thermodynamic instability near the transition. This instability is reduced by pressure which drives a genuine Mott transition to an eventually homogeneous metallic state.