Ginzburg-Landau theory of metal-insulator transition in VO₂: The electronic degrees of freedom

VO₂ is a well-known strongly correlated system which exhibits an intriguing metal-insulator transition slightly above room temperature. Based on symmetry consideration, we propose a phenomenological Ginzburg-Landau potential incorporating both a structural order parameter and a spin-correlation order parameter, to explicitly capture the structural distortion and the electronic phase transition in VO₂. With the help of the additional spin-correlation order parameter, we calculate consistently temperature-stress (strain) phase diagrams of VO₂ under different mechanical boundary conditions, which show good agreement with existing experimental observations. The phenomenological potential is suitable for the implementation in phase-field simulations to further investigate the stable phases, morphology and evolution of domain structures under various mechanical and electrical stimuli.