High-Harmonic Spectroscopy of Coherent Lattice Dynamics in Graphene

TL;DR

This paper demonstrates how high-harmonic spectroscopy can be used to detect and analyze the influence of coherent lattice vibrations, specifically phonon modes, on the electronic response in graphene with ultrafast temporal resolution.

Contribution

It introduces the application of high-harmonic spectroscopy to study coherent phonon effects on electronic dynamics in graphene, revealing spectral sidebands linked to phonon modes.

Findings

Coherent phonon excitation produces sidebands in harmonic spectra.

Spectral positions and polarization of sidebands reveal phonon-induced symmetry changes.

High-harmonic spectroscopy provides sub-femtosecond temporal resolution for phonon-electron interactions.

Abstract

High-harmonic spectroscopy of solids is a powerful tool, which provides access to both electronic structure and ultrafast electronic response of solids, from their band structure and density of states, to phase transitions, including the emergence of the topological edge states, to the PetaHertz electronic response. However, in spite of these successes, high harmonic spectroscopy has hardly been applied to analyse the role of coherent femtosecond lattice vibrations in the attosecond electronic response. Here we study coherent phonon excitations in monolayer graphene to show how high-harmonic spectroscopy can be used to detect the influence of coherent lattice dynamics, particularly longitudinal and transverse optical phonon modes, on the electronic response. Coherent excitation of the in-plane phonon modes results in the appearance of sidebands in the spectrum of the emitted harmonic radiation. We show that the spectral positions and the polarisation of the sideband emission offer a sensitive probe of the dynamical symmetries associated with the excited phonon modes. Our work brings the key advantage of high harmonic spectroscopy -- the combination of sub-femtosecond to tens of femtoseconds temporal resolution -- to the problem of probing phonon-driven electronic response and its dependence on the dynamical symmetries in solids.