Terahertz displacive excitation of a coherent Raman-active phonon in V2O3
F. Giorgianni, Mattia Udina, Tommaso Cea, E. Paris, Marco Caputo, M. Radović, Larissa Boie, Joe Sakai, C. Schneider, Steven L. Johnson
Abstract
Abstract Nonlinear processes involving frequency-mixing of light fields set the basis for ultrafast coherent spectroscopy of collective modes in solids. In certain semimetals and semiconductors, generation of coherent phonon modes can occur by a displacive force on the lattice at the difference-frequency mixing of a laser pulse excitation on the electronic system. Here, as a low-frequency counterpart of this process, we demonstrate that coherent phonon excitations can be induced by the sum-frequency components of an intense terahertz light field, coupled to intraband electronic transitions. This nonlinear process leads to charge-coupled coherent dynamics of Raman-active phonon modes in the strongly correlated metal V 2 O 3 . Our results show an alternative up-conversion pathway for the optical control of Raman-active modes in solids mediated by terahertz-driven electronic excitation.