Orbital magnetism in an electric field-driven Mott insulator*

Motivated by the recent discovery of electric field-induced strong diamagnetism
in a Mott insulator Ca₂RuO₄ [1], we use the gauge invariant Keldysh Green function
formalism to investigate the roles of electric field in the orbital magnetism of a two-band
Mott insulator. We first generalize the Landau-Peierls formula for orbital susceptibility to
account for both inter-band and nonequilibrium effects. We find that the electric field
induces an over-population of hot electrons due to Joule heating and reduces the band gap.
This drives the system closer to a semimetallic state with light mass conduction electrons,
and leads to an enhancement of diamagnetism.



[1] C. Sow, S. Yonezawa, S. Kitamura, T. Oka, K. Kuroki, F. Nakamura, and Y. Maeno,
Science 358, 1084 (2017).