AI Article Synopsis
- Femtosecond X-ray pulses excite electrons in solids and lead to energy transfer between the electrons and the lattice, causing heating over a few hundred femtoseconds.
- Experiments using X-ray free-electron lasers have revealed insights into how these electrons thermalize, particularly in materials like GaAs.
- This study proposes a theoretical framework to explain unexpected changes in optical reflectivity related to band-gap shrinking and predicts electron-lattice thermalization timescales in high-energy conditions, encouraging further research in similar semiconductor systems.
Article Abstract
Femtosecond X-ray irradiation of solids excites energetic photoelectrons that thermalize on a timescale of a few hundred femtoseconds. The thermalized electrons exchange energy with the lattice and heat it up. Experiments with X-ray free-electron lasers have unveiled so far the details of the electronic thermalization. In this work we show that the data on transient optical reflectivity measured in GaAs irradiated with femtosecond X-ray pulses can be used to follow electron-lattice relaxation up to a few tens of picoseconds. With a dedicated theoretical framework, we explain the so far unexplained reflectivity overshooting as a result of band-gap shrinking. We also obtain predictions for a timescale of electron-lattice thermalization, initiated by conduction band electrons in the temperature regime of a few eVs. The conduction and valence band carriers were then strongly non-isothermal. The presented scheme is of general applicability and can stimulate further studies of relaxation within X-ray excited narrow band-gap semiconductors.
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| http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4676029 | PMC |
| http://dx.doi.org/10.1038/srep18068 | DOI Listing |
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