Coherent Phonon Coupling to Individual Bloch States in Photoexcited Bismuth

TL;DR

This study uses time-resolved photoelectron spectroscopy to explore how coherent phonons influence electronic states in photoexcited bismuth, revealing wavevector-dependent oscillations and temperature-related shifts.

Contribution

It demonstrates the wavevector dependence of phonon-induced oscillations and distinguishes bulk from surface state responses in bismuth.

Findings

Bulk-like bands oscillate with the A1g phonon frequency.

Surface states are insensitive to coherent lattice displacements.

Electronic states shift in energy following electronic temperature changes.

Abstract

We investigate the temporal evolution of the electronic states at the bismuth (111) surface by means of time and angle resolved photoelectron spectroscopy. The binding energy of bulk-like bands oscillates with the frequency of the $A_{1g}$ phonon mode whereas surface states are insensitive to the coherent displacement of the lattice. A strong dependence of the oscillation amplitude on the electronic wavevector is correctly reproduced by \textit{ab initio} calculations of electron-phonon coupling. Besides these oscillations, all the electronic states also display a photoinduced shift towards higher binding energy whose dynamics follows the evolution of the electronic temperature.