# Ultrafast Electron-Lattice Coupling Dynamics in VO2 and V2O3 Thin Films

## TL;DR

This study uses ultrafast spectroscopy to investigate electron-lattice interactions in VO2 and V2O3 thin films, revealing strong electron-phonon coupling, temperature-dependent sound velocities, and strain effects in their metallic phases.

## Contribution

It provides the first detailed comparison of ultrafast electron-lattice dynamics in VO2 and V2O3 using optical and terahertz spectroscopy over a wide temperature range.

## Key findings

- Strong electron-phonon coupling in metallic phases
- Temperature-dependent sound velocity increases by 4-5 times in VO2 and 3-5 times in V2O3
- Ultrafast strain control affects V2O3 more than VO2

## Abstract

Ultrafast optical pump - optical probe and optical pump - terahertz probe spectroscopy were performed on vanadium dioxide (VO2) and vanadium sesquioxide (V2O3) thin films over a wide temperature range. A comparison of the experimental data from these two different techniques and two different vanadium oxides, in particular a comparison of the electronic oscillations generated by the photoinduced longitudinal acoustic modulation, reveals the strong electron-phonon coupling that exists in the metallic state of both materials. The low energy Drude response of V2O3 appears more susceptible than VO2 to ultrafast strain control. Additionally, our results provide a measurement of the temperature dependence of the sound velocity in both systems, revealing a four- to fivefold increase in VO2 and a three- to fivefold increase in V2O3 across the phase transition. Our data also confirm observations of strong damping and phonon anharmonicity in the metallic phase of VO2, and suggest that a similar phenomenon might be at play in the metallic phase of V2O3. More generally, our simple table-top approach provides relevant and detailed information about dynamical lattice properties of vanadium oxides, opening the way to similar studies in other complex materials.