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01.02.2019

IMN-Sonderkolloquium: "Ultrafast dynamics of hot charge carriers and polariton condensates in ZnO"

Am Freitag, dem 01.02.2019, um 10.00 Uhr spricht Dr. Rüdiger Schmidt-Grund von der Universität Leipzig, Fakultät für Physik und Geowissenschaften, Institut für Experimentelle Physik II, Halbleiterphysik, im Rahmen des IMN-Sonderkolloquiums zum Thema ""Ultrafast dynamics of hot charge carriers and polariton condensates in ZnO"". Die Veranstaltung findet im Feynmanbau, Gustav-Kirchhoff-Straße 7, Raum 114/115, statt.

Zum Vortrag:
I will discuss the fs-dynamics of hot charge carriers and phonons in the wide gap semiconductor ZnO after intense optical excitation as observed in the transient dielectric function, probed by femtosecond time resolved pump-probe spectroscopic ellipsometry. In the sub-ps range we observe partial blocking and screening of near-gap and exciton absorption due to occupation of the conduction band by hot electrons. At the same time, intra valence band transitions occur when holes scatter to the edges of the Brillouin zone. The subsequent carrier relaxation in the ps time range is governed by hot phonon effects. The final heat transfer to the lattice continues up to the nanoseconds-time-scale. The dynamics of the dielectric function and charge carriers also rule properties of lasing, which I will demonstrate by some examples with ZnO nano- and microscale microcavities. Mainly, onset of lasing is determined by the carrier relaxation down to the conduction band minimum while the spectral occurrence of lasing modes and their shift in time is ruled by the dielectric function dynamics. I will further demonstrate the ps spatio-temporal evolution of polariton Bose-Einstein condensates in a wire microcavity.

Gäste sind herzlich willkommen.