Terahertz displacive excitation of a coherent Raman-active phonon in V$_2$O$_3$

TL;DR

This paper demonstrates that intense terahertz light fields can induce coherent Raman-active phonons in V₂O₃ through a sum-frequency nonlinear process, revealing a new pathway for optical control of lattice vibrations in correlated materials.

Contribution

It introduces a novel terahertz-driven up-conversion mechanism to excite Raman-active phonons via electronic intraband transitions in V₂O₃.

Findings

Coherent phonons can be generated by terahertz sum-frequency components.

The process couples electronic excitation with lattice dynamics.

It offers a new method for optical control of phonons in correlated materials.

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 a new up-conversion pathway for the optical control of Raman-active modes in solids mediated by terahertz-driven electronic excitation.