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arXiv · 2308.05803

Nature of the current-induced insulator-to-metal transition in Ca$_2$RuO$_4$ as revealed by transport-ARPES

Cissy T Suen·Igor Marković·Marta Zonno·Niclas Heinsdorf·Sergey Zhdanovich·Na-Hyun Jo·Michael Schmid·Philipp Hansmann·Pascal Puphal·Katrin Fürsich·Valentin Zimmerman·Steef Smit·Christine Au-Yeung·Berend Zwartsenberg·Maximilian Krautloher·Ilya S Elfimov·Roland Koch·Sergey Gorovikov·Chris Jozwiak·Aaron Bostwick·Marcel Franz·Eli Rotenberg·Bernhard Keimer·Andrea Damascelli
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Abstract

The Mott insulator Ca$_2$RuO$_4$ exhibits a rare insulator-to-metal transition (IMT) induced by DC current. While structural changes associated with this transition have been tracked by neutron diffraction, Raman scattering, and x-ray spectroscopy, work on elucidating the response of the electronic degrees of freedom is still in progress. Here we unveil the current-induced modifications of the electronic states of Ca$_2$RuO$_4$ by employing angle-resolved photoemission spectroscopy (ARPES) in conjunction with four-probe transport. Two main effects emerge: a clear reduction of the Mott gap and a modification in the dispersion of the Ru-bands. The changes in dispersion occur exclusively along the $XM$ high-symmetry direction, parallel to the $b$-axis where the greatest in-plane lattice change occurs. These experimental observations, together with dynamical mean-field theory (DMFT) calculations simulated from the current-induced structural distortions, indicate the intimate interplay of lattice and orbital-dependent electronic response in the current-driven IMT. Furthermore, based on a free energy analysis, we demonstrate that the current-induced phase, albeit thermodynamically equivalent, is electronically distinct from the high-temperature zero-current metallic phase. Our results provide insight into the elusive nature of the current-induced IMT of Ca$_2$RuO$_4$ and advance the challenging, yet powerful, technique of transport-ARPES.

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Cissy T Suen, Igor Marković, Marta Zonno, Niclas Heinsdorf, Sergey Zhdanovich, Na-Hyun Jo, Michael Schmid, Philipp Hansmann, Pascal Puphal, Katrin Fürsich, Valentin Zimmerman, Steef Smit, Christine Au-Yeung, Berend Zwartsenberg, Maximilian Krautloher, Ilya S Elfimov, Roland Koch, Sergey Gorovikov, Chris Jozwiak, Aaron Bostwick, Marcel Franz, Eli Rotenberg, Bernhard Keimer, Andrea Damascelli. 2023-08-10. Nature of the current-induced insulator-to-metal transition in Ca$_2$RuO$_4$ as revealed by transport-ARPES. https://doi.org/10.1038/s41567-024-02629-3

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