Coherent Phonon Coupling to Individual Bloch States in Photoexcited Bismuth

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 bulklike 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 wave vector is correctly reproduced by 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.

Direct observation of electron thermalization and electron-phonon coupling in photoexcited bismuth

“…While in previous work we have examined the wave vector dependence of electron-phonon coupling, 19 we focus here on the dependence of electron-phonon coupling with the band index. The experimental results of fig.…”

“…19). Figure 6a) shows the evolution of the electron temperature as a function of pump-probe delay for a incident pump fluence of 0.16 mJ/cm 2 .…”

Wannier interpolation of the electron-phonon matrix elements in polar semiconductors: Polar-optical coupling in GaAs

“…The interpretation and analysis of the (ultra)fast dynamics of relaxation of photoexcited electrons is particularly difficult, because many relaxation processes are present simultaneously, and disentangling their respective contributions requires ad hoc information on their relative importance and order of magnitude 9 . At the same time, ab initio calculations provide an effective tool to estimate electron-phonon coupling strength in metals [10][11][12] and semimetals like graphene [13][14][15][16] or bismuth 17,18 . In the case of semiconductors, the predictive capability of calculations based on density functional perturbation theory (DFPT) 19,20 for the electronphonon matrix elements has been demonstrated in a number of semiconductors [21][22][23] , alloys 24,25 and nanostructures 23,26 .…”

First-Principles Calculation of Femtosecond Symmetry-Breaking Atomic Forces in Photoexcited Bismuth

“…Here the "single Fermi-Dirac" occupation refers to the approach used in Refs. [14][15][16], where the excited electron-hole distribution is represented by occupying the electronic states with a high-temperature Fermi-Dirac distribution. The occupation scheme referred to as "two chemical potential" was used in Ref.…”

“…There have been several theoretical investigations of the DECP mechanism driving the A 1g mode in recent years [10,[14][15][16] and all have shown excellent agreement between their density functional theory (DFT) based predictions and experimental measurements despite various approaches to treating the excited electron-hole plasma used in different theoretical studies. However, a quantitative first-principles analysis of the mechanism driving the lower-symmetry E g mode has thus far been lacking.…”