Probing Phonon dynamics and Electron-Phonon Coupling by High Harmonic Generation in Solids

TL;DR

This paper demonstrates that high harmonic generation (HHG) in solids can be used to probe phonon dynamics and electron-phonon coupling, providing a new all-optical method for characterizing material properties.

Contribution

It introduces a novel approach to extract phonon information and electron-phonon couplings from HHG spectra in solids, which was previously neglected.

Findings

Phonon deformation affects HHG signals.

HHG can reveal mode-resolved electron-phonon couplings.

Method is suitable for materials under high pressure or with gapped states.

Abstract

Acting as a highly nonlinear response to the strong laser field, high harmonic generation (HHG) naturally contains the fingerprints of atomic and electronic properties of materials. Electronic properties of a solid such as band structure and topology can thus be probed, while the phonon dynamics during HHG are often neglected. Here we show that by exploiting the effects of phonon deformation on HHG, the intrinsic phonon information can be deciphered and direct probing of band- and mode-resolved electron-phonon couplings (EPC) of photoexcited materials is possible. Considering HHG spectroscopy can be vacuum free and unrestricted to electron occupation, this work suggests HHG is promising for all-optical characterization of EPC in solids, especially for gapped quantum states or materials under high pressure.