electric control of the structural properties of spin-orbit coupled 4<i>d</i> ruthenate Ca₂Ru_0.97Mn_0.03O₄

The unique competition between spin-orbit interaction (SOI) and Coulomb correlation (U) in 4d/5d oxides drives unusual physical behavior. Novel nonequilibrium phenomena can be further induced by external stimuli including intense synchrotron x-ray or electric current. In this talk, we report neutron diffraction study of the quasi-two-dimensional Mott Ca₂Ru_0.97Mn_0.03O₄, which shows dramatic reduction of the electric resistivity, suppression of the antiferromagnetic transition, and induction of new orbital order with critical current density of 0.15 A/cm². Our in-situ structural characterization implies that the in-plane orthorhombicity diminishes with increasing current density, accompanied by the straightened of the Ru-O-Ru bonding angles. The temperature-current phase diagram establishes an intimate correlation between the lattice and electronic structure in this nonequilibrium, steady state driven by current. Our results shed light to the nature of the Mott-Insulator transition and provide key information for the emerging phenomena near the transition.