Ultrafast Relaxation of Symmetry-Breaking Photo-Induced Atomic Forces

We present a first-principles method for the calculation of the temperature-dependent relaxation of symmetry-breaking atomic driving forces in photoexcited systems. We calculate the phonon-assisted decay of the photoexcited force on the low-symmetry E_{g} mode following absorption of an ultrafast pu...

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Bibliographic Details
Published in:Physical review letters 2019-08, Vol.123 (8), p.087401-087401, Article 087401
Main Authors: O'Mahony, Shane M, Murphy-Armando, Felipe, Murray, Éamonn D, Querales-Flores, José D, Savić, Ivana, Fahy, Stephen
Format: Article
Language:English
Subjects:
Antimony
Bismuth
Broken symmetry
Decay rate
First principles
Mathematical analysis
Phonons
Photons
Symmetry
Temperature dependence
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Summary:We present a first-principles method for the calculation of the temperature-dependent relaxation of symmetry-breaking atomic driving forces in photoexcited systems. We calculate the phonon-assisted decay of the photoexcited force on the low-symmetry E_{g} mode following absorption of an ultrafast pulse in Bi, Sb, and As. The force decay lifetimes for Bi and Sb are of the order of 10 fs and in agreement with recent experiments, demonstrating that electron-phonon scattering is the primary mechanism relaxing the symmetry-breaking forces. Calculations for a range of absorbed photon energies suggest that larger amplitude, symmetry-breaking atomic motion may be induced by choosing a pump photon energy which maximizes the product of the initial E_{g} force and its lifetime. The high-symmetry A_{1g} force undergoes a partial decay to a nonzero constant on similar timescales, which has not yet been measured in experiments. The average imaginary part of the electron self-energy over the photoexcited carrier distribution provides a crude indication of the decay rate of symmetry-breaking forces.
ISSN:0031-9007
1079-7114
DOI:10.1103/PhysRevLett.123.087401