Regensburg 2022 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 30: Semiconductor Surfaces
O 30.1: Topical Talk
Dienstag, 6. September 2022, 10:30–11:00, S053
Surface Phase Transitions in Atomistic Detail and with Femtosecond Resolution — •Wolf Gero Schmidt — Universität Paderborn
Ab initio molecular dynamics on ground and excited-state potential energy surfaces may be used to gain deep insight in the driving forces and mechanisms of surface phase transitions and can greatly assist the interpretation of experimental data. This is illustrated in my talk using two prominent examples: (i) Photoholes localized at the Brillouin zone boundary of the In/Si(111)(8x2) surface are shown to drive an ultrafast (8x2) —→ (4x1) phase change that is accompanied by an insulator-metal transition [1,2]. (ii) Thermal excitation of the Au/Si(553)(1x6) surface leads to soft Au chain vibrations that reduce transiently the Au electron affinity, which lowers the barrier for a sp2 + p —→ sp3 hybridization change of Si step edge atoms. This leads eventually to an order-disorder phase transition and the formation of a two-dimensional spin liquid [3].
[1] T Frigge et al., Nature 544, 207 (2017).
[2] CW Nicholson et al., Science 362, 821 (2018).
[3] C Braun et al., PRL 124, 146802 (2020).