Universal size-dependent nonlinear charge transport in single crystals of the Mott insulator Ca$_2$RuO$_4$

Guerino Avallone; Remko Fermin; Kaveh Lahabi; Veronica Granata; Rosalba Fittipaldi; Carla Cirillo; Carmine Attanasio; Antonio Vecchione; Jan Aarts

doi:10.1038/s41535-021-00394-7

arXiv · 2102.06556

Universal size-dependent nonlinear charge transport in single crystals of the Mott insulator Ca$_2$RuO$_4$

Guerino Avallone·Remko Fermin·Kaveh Lahabi·Veronica Granata·Rosalba Fittipaldi·Carla Cirillo·Carmine Attanasio·Antonio Vecchione·Jan Aarts

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Abstract

The surprisingly low current density required for inducing the insulator to metal transition has made Ca$_2$RuO$_4$ an attractive candidate material for developing Mott-based electronics devices. The mechanism driving the resistive switching, however, remains a controversial topic in the field of strongly correlated electron systems. Here we probe an uncovered region of phase space by studying high-purity Ca$_2$RuO$_4$ single crystals, using the sample size as principal tuning parameter. Upon reducing the crystal size, we find a four orders of magnitude increase in the current density required for driving Ca$_2$RuO$_4$ out of the insulating state into a non-equilibrium (also called metastable) phase which is the precursor to the fully metallic phase. By integrating a microscopic platinum thermometer and performing thermal simulations, we gain insight into the local temperature during simultaneous application of current and establish that the size dependence is not a result of Joule heating. The findings suggest an inhomogeneous current distribution in the nominally homogeneous crystal. Our study calls for a reexamination of the interplay between sample size, charge current, and temperature in driving Ca$_2$RuO$_4$ towards the Mott insulator to metal transition.

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Guerino Avallone, Remko Fermin, Kaveh Lahabi, Veronica Granata, Rosalba Fittipaldi, Carla Cirillo, Carmine Attanasio, Antonio Vecchione, Jan Aarts. 2021-02-12. Universal size-dependent nonlinear charge transport in single crystals of the Mott insulator Ca$_2$RuO$_4$. https://doi.org/10.1038/s41535-021-00394-7

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