Ultrafast spectroscopy of coherent phonons across the pressure driven insulator to metal phase transition in V2O3

Nowadays, materials science is moving towards the understanding and control of materials in nonequilibrium states by making use of perturbative techniques to investigate their dynamical responses. From this perspective, the use of ultrashort light pulses seems to be a relevant approach as it can selectively address different degrees of freedom in solid-state systems and more particularly electrons. Such a method can help to decipher the physical phenomena arising from electronic correlations and complements a more conventional methodology where the phase diagrams of materials are investigated at thermodynamical equilibrium. Here, we combine femtosecond optical spectroscopy and a high-pressure setup to monitor the ultrafast out-of-equilibrium photo response of a V2O3 thin film across the pressure driven insulator-to-metal transition. The experimental results demonstrate the possibility to use the spectroscopy of coherent phonons as a thermodynamical phase marker in V2O3 thin films. In addition, the frequency behavior of the ultrafast coherent phonon mode (A1g character) seems to reflect the manifestation of a strong coupling between the lattice and electronic degrees of freedom near first-order transition lines with a pronounced drop in frequency around the critical pressure.