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HL: Fachverband Halbleiterphysik

HL 23: Ultra-fast phenomena

HL 23.4: Vortrag

Dienstag, 17. März 2020, 10:15–10:30, POT 112

Comparison of atomic pathways during nonthermal melting in the isostructural elements germanium and silicon — •Tobias Zier and Martin Garcia — Theoretische Physik, Universität Kassel, Heinrich-Plett-Str. 40, 34132 Kassel, Germany

Intense femtosecond-laser pulses can induce extreme non-equilibrium conditions in solids. As a consequence the crystalline structure of the solid exhibits nonthermal effects, like, coherent phonons, thermal phonon squeezing, or nonthermal melting. In the latter case the interatomic bonding is broken by the laser pulse, which excites a large amount of electrons from bonding into antibonding states. The ensuing atomic forces, that raise because of the change in the interatomic bonding, accelerate the atoms away from their initial positions. In a recent publication we could resolve the atomic motions and pathways during nonthermal melting in silicon by performing molecular dynamics simulations using our own electronic-temperature density-functional theory code CHIVES.[1] Here, we study the atomic motion during nonthermal melting in the isostructural element germanium, which has almost the same lattice parameter than silicon but less strong interatomic bonding. We will identify the most important melting directions and compare them to the results found in silicon, in order to find similarities and/or differences in the underlying melting mechanism. Our findings will help to find a general theory that describes the atomic pathways during nonthermal melting.

[1] T. Zier, E. S. Zijlstra, M. E. Garcia, Phys. Rev. Lett. 116, 153901 (2016).