Nature of the photoinduced metallic state in monoclinic ${\mathrm{VO}}_2$

The metal-insulator transition of ${\mathrm{VO}}_2$, which in equilibrium is associated with a structural phase transition, has been intensively studied for decades. It is challenging to disentangle the role of Mott physics from dimerization effects in the insulating phase. Femtosecond time-resolved experiments showed that optical excitations can induce a transient metallic state in the dimerized phase, which is distinct from the known equilibrium phases. In this letter, we combine nonequilibrium cluster dynamical mean-field theory with realistic first-principles modeling to clarify the nature of this laser-induced metallic state. We show that the doublon-holon production by laser pulses with polarization along the V-V dimers and the subsequent interorbital reshuffling of the photocarriers leads to a population of orbital-mixed states and the filling of the gap. The photoinduced metal state is qualitatively like a hot electronic state in the dimerized structure and does not involve a collapse of the Mott gap.