First-order melting of a weak spin-orbit Mott insulator into a correlated metal

TL;DR

This study maps the phase transitions in a weak spin-orbit Mott insulator as it dopes into a correlated metal, revealing a first-order transition and nanoscale phase separation.

Contribution

It provides the first detailed experimental phase diagram of (Sr(1-x)Lax)3Ir2O7, highlighting the nature of the insulator-metal transition and associated phase coexistence.

Findings

Immediate resistivity collapse with doping

Nanoscale phase separation persists until x~0.04

First-order transition to a homogeneous metallic state

Abstract

The electronic phase diagram of the weak spin-orbit Mott insulator (Sr(1-x)Lax)3Ir2O7 is determined via an exhaustive experimental study. Upon doping electrons via La substitution, an immediate collapse in resistivity occurs along with a narrow regime of nanoscale phase separation comprised of antiferromagnetic, insulating regions and paramagnetic, metallic puddles persisting until x~0.04. Continued electron doping results in an abrupt, first-order phase boundary where the Neel state is suppressed and a homogenous, correlated, metallic state appears with an enhanced spin susceptibility and local moments. As the metallic state is stabilized, a weak structural distortion develops and suggests a competing instability with the parent spin-orbit Mott state.