Differentiating Photoexcited Carrier and Phonon Dynamics in the {\Delta}, L, and {\Gamma} Valleys of Si(100) with Transient Extreme Ultraviolet Spectroscopy

TL;DR

This study uses transient XUV spectroscopy to investigate how core-hole effects influence the measurement of photoexcited carrier dynamics in silicon, revealing the importance of many-body models for accurate interpretation.

Contribution

It introduces a comprehensive model based on many-body approximations and the Bethe-Salpeter equation to interpret transient XUV spectra in photoexcited semiconductors.

Findings

Core-hole effects partially obscure electron and hole energy measurements.

The model accurately predicts time constants matching known scattering times.

Transient spectra interpretation benefits from advanced many-body theoretical frameworks.

Abstract

Transient extreme ultraviolet (XUV) spectroscopy probes core level transitions to unoccupied valence and conduction band states. Uncertainty remains to what degree the core-hole created by the XUV transition modifies the measurement of photoexcited electron and hole energies. Here, the Si {\L_{2,3}} edge is measured after photoexcitation of electrons to the {\Delta}, L, and {\Gamma} valleys of Si(100). The measured changes in the XUV transition probability do not energetically agree with the increasing electron photoexcitation energy. The data therefore experimentally confirm that, for the Si {\L_{2,3}} edge, the time-dependent electron and hole energies are partially obscured by the core-hole perturbation. A model based on many-body approximations and the Bethe-Salpeter equation is successfully used to predict the core-hole{\apos}s modification of the final transition density of states in terms of both electronic and structural dynamics. The resulting fit time constants match the excited state electron thermalization time and the inter-valley electron-phonon, intra-valley electron-phonon, and phonon-phonon scattering times previously measured in silicon. The outlined approach is a more comprehensive framework for interpreting transient XUV absorption spectra in photoexcited semiconductors.