Dresden 2017 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 75: Poster Session: Transport 1
TT 75.21: Poster
Donnerstag, 23. März 2017, 15:00–19:00, P2-EG
Beyond the Born-Oppenheimer approximation: Non-adiabatic processes in manganites — •Michael ten Brink1, Peter E. Blöchl2, Stephanie Mildner3, and Christian Jooss3 — 1Institute for Theoretical Physics, University of Goettingen — 2Institute for Theoretical Physics, Clausthal University of Technology — 3Institute for Materials Physics, University of Goettingen
Non-adiabatic processes in the combined atomic and electronic dynamics are explored using two simple model systems, the Holstein model and the Jahn-Teller model. Numerically exact simulations demonstrate processes for the optical excitation and the subsequent relaxation into the ground state. The Holstein model is the classical model for polarons and its dimer allows to demonstrate the role of electronic and structural transitions in an optical excitation. We demonstrate (1) predominantly electronic interband excitations, which are Frank-Condon like, (2) predominantly structural intra-band transitions related to tunnel processes, and (3) an electronic transition that critically depends on the presence of thermal phonons. The latter gives rise to a distinct absorption band with strong temperature dependence. The dominant relaxation mechanisms lead through conical intersections, for which the Jahn-Teller model is the classical model system. We present the transition of a quantum mechanical, nuclear-electronic wave packet through the conical intersection. We discuss the results of measured optical absorption spectra in manganites in view of our theoretical findings.
This work is supported by the Deutsche Forschungsgemeinschaft via SFB 1073 through projects B03 and C03.