Current-induced successive structural phase transitions beyond thermal equilibrium in single-crystal VO2

Abstract: Nonequilibrium systems driven by external energy sources host unexplored physics; yet phase transitions beyond thermal equilibrium remain elusive. Here, we demonstrate that electric current induces structural phase transitions in single-crystal VO2, a prototypical strongly correlated material. At room temperature, synchrotron X-ray diffraction shows that a current density of 6.5 A/cm2 disrupts V-V dimers, driving a monoclinic-to-tetragonal insulator-to-metal transition, independent of Joule heating. Increasing the current to 10 A/cm2 triggers a discontinuous isotropic lattice expansion, stabilizing a novel tetragonal structure that does not exist in thermal equilibrium. Optical microscopy and microscopic Raman spectroscopy reveal dynamic domain motion and metastable phases, reminiscent of dissipative structures. These findings establish direct pathways to access hidden phases and symmetry changes beyond thermal equilibrium, broadening the frontiers of nonequilibrium thermodynamics.