Current-Induced Gap Suppression in the Mott Insulator Ca$_2$RuO$_4$

TL;DR

This study investigates how high currents can suppress the electronic gap in the Mott insulator Ca$_2$RuO$_4$, revealing nonlinear conduction behaviors and proposing a current-induced gap suppression mechanism.

Contribution

The paper introduces a precise measurement approach to evaluate self-heating effects and demonstrates a novel current-induced gap suppression in Ca$_2$RuO$_4$, distinct from conventional mechanisms.

Findings

Resistivity decreases with current under isothermal conditions.

Nonlinear conduction and negative differential resistance occur at low currents.

Proposes a current-induced gap suppression scenario in Mott insulators.

Abstract

We present nonlinear conduction phenomena in the Mott insulator Ca2RuO4 investigated with a proper evaluation of self-heating effects. By utilizing a non-contact infrared thermometer, the sample temperature was accurately determined even in the presence of large Joule heating. We find that the resistivity continuously decreases with currents under an isothermal environment. The nonlinearity and the resulting negative differential resistance occurs at relatively low current range, incompatible with conventional mechanisms such as hot electron or impact ionization. We propose a possible current-induced gap suppression scenario, which is also discussed in non-equilibrium superconducting state or charge-ordered insulator.