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K: Fachverband Kurzzeitphysik

K 4: Laser-Materie-Wechselwirkung und Laseranwendungen I

K 4.3: Vortrag

Dienstag, 18. März 2014, 11:45–12:00, SPA SR203

Nonthermal melting in semiconductors under X-ray free-electron laser pulse irradiation — •Nikita Medvedev¹, Harald Jeschke², and Beata Ziaja¹ — ¹Center for Free-Electron Laser Science, Deutsches Elektronen-Synchrotron DESY, Notkestrasse 85, D-22607 Hamburg, Germany — ²Institut für Theoretische Physik, Goethe-Universität Frankfurt am Main, Max-von-Laue-Strasse 1, D-60438 Frankfurt, Germany

After irradiation of a covalently bonded material with a femtosecond intense X-ray pulse, one can observe an ultrafast nonthermal melting occurring on sub-picosecond timescale. Such melting is induced by a modification of the interatomic potential, triggered by the electron excitation. We studied such process in detail with newly developed hybrid approach MC-TBMD [1-3]. It revealed the multistep nature of the nonthermal melting: an interplay between the high-energy electron relaxation, bandgap collapse and modification of the electronic structure, and atomic relaxation into the new phase. We calculated the damage threshold of the nonthermal graphitization of diamond as a function of photon energy within a wide energy range: from a few eV up to tens of keV [2,3]. It appeared that the higher the photon energy, the longer it takes for the atomic relaxation and the subsequent phase transition [3].

[1] N. Medvedev, H. Jeschke, B. Ziaja, New J. Phys. 15, 015016 (2013)

[2] J. Gaudin et al., Phys. Rev. B 88, 060101 (2013)

[3] N. Medvedev, H. Jeschke, B. Ziaja, Phys. Rev. B (2013 in press)