Earnshaw Medal
Earnshaw 2009 Nominees: Donal O’Donoghue, UCC
Classical simulation of optically excited phonon dynamics in Bismuth
This report documents the research I undertook as part of my final year project in the Single Honours BSc in Physics in University College Cork. Professor Stephen Fahy of the Condensed Matter Theory group was my supervisor for the duration of this project. The work outlined in this document is a result of our combined efforts on this project. We endeavored to carry out a full dynamical simulation of photo-excited atomic oscillations in Bismuth using classical dynamics, on the picosecond time scale. We were particularly interested in the rate of decay of the A1g phonon mode in Bismuth. The lifetime of the A1g mode has previously been measured experimentally, with the aid of optical “pump-probe” experiments, and calculated theoretically using density functional perturbation theory. We will compare the lifetime of this mode as determined by our classical simulation, with the corresponding times found in previous works, both experimental and theoretical. We will also investigate with our simulation to what extend this lifetime depends on factors such as initial amplitude and electron-hole plasma density. In this report we will emphasize the computational and numerical nature of the research being undertaken, and we will describe the process of creating a working dynamical simulation in some detail.
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