Emergence of a metallic meta-stable phase induced by electrical current in Ca_2RuO_4

TL;DR

This study reveals that applying electrical current to Ca_2RuO_4 induces a metastable metallic phase within its insulating state, explaining unusual electrical behaviors through combined macroscopic and microscopic analyses.

Contribution

It demonstrates the emergence of a metastable metallic phase in Ca_2RuO_4 under current bias, combining transport and X-ray diffraction to uncover its properties and origins.

Findings

A resistivity map showing the current-induced phase transition.

Identification of a metastable metallic phase coexisting with insulating and metallic phases.

Explanation of negative differential resistivity through the properties of the metastable phase.

Abstract

A comprehensive study of the behavior of the Mott insulator Ca_2RuO_4 under electrical current drive is performed by combining two experimental probes: the macroscopic electrical transport and the microscopic X-Ray diffraction. The resistivity, rho, vs electric current density, J, and temperature, T , rho(J,T), resistivity map is drawn. In particular, the meta-stable state, induced between the insulating and the metallic thermodynamic states by current biasing Ca_2RuO_4 single crystals, is investigated. Such an analysis, combined with the study of the resulting RuO_6 octahedra energy levels, reveals that a metallic crystal phase emerges in the meta-stable regime. The peculiar properties of such a phase, coexisting with the well-established orthorhombic insulating and tetragonal metallic phases, allow to explain some of the unconventional and puzzling behaviors observed in the experiments, as a negative differential resistivity.