Band structure effects of a current-induced Mott-insulator to metal transition in Ca₂RuO₄

The Mott insulator Ca₂RuO₄ can be turned into a metal by the application of a weak electric field and a corresponding transport current. This transition affects the optical and magnetic properties of the material. However, because of the electric field's presence and the field-induced energy broadening, it is challenging to determine the electronic structure in the metallic state by angle-resolved photoemission spectroscopy (ARPES). Making use of the recently introduced approach to enable ARPES measurements of current-carrying devices by using a nano-scale light spot [1], we are able to measure ARPES data that tracks the current-induced phase transition in Ca₂RuO₄ simultaneously with the electrical transport, revealing the spectral function of the current-induced state along with a potential map of the sample's surface.

[1] D. Curcio et al., Phys. Rev. Lett. 125, 236403 (2020).