Imaging the current-driven metal–insulator transition in Ca₂RuO₄

The flow of electric current is a powerful tool to alter the ground state of strongly correlated ruthenates, where novel material properties emerge in non-equilibrium steady states [1,2,3]. Despite the efforts to investigate these phenomena, the microscopic mechanism and the physical quantities responsible for the current-induced phase changes have not been clarified yet.
Here, I will present our recent results based on thermal imaging of single-crystal Ca₂RuO₄ while triggering its metal–insulator transition with the flow of direct current. By measuring the infrared thermal emission of the material and exploiting the different emissivity of the metallic and insulating state, we observe the formation of phase-separated regions which can be controlled and stabilised by current. We determine the correlation between current density and the metal–insulator transition, discussing the interplay between electronic effects and localised Joule heating. Our technique provides a fundamental step towards understanding the mechanism regulating current-induced phenomena in quantum materials.

[1] Sow, et al., Science 358, 6366 (2017)
[2] Zhang, et al., Phys. Rev. X 9,011032 (2019)
[3] Nakamura, et al., Sci. Rep. 3, 2536 (2013)