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DY: Fachverband Dynamik und Statistische Physik

DY 20: Glasses I (jointly with DF and CPP)

DY 20.8: Vortrag

Mittwoch, 16. März 2011, 12:00–12:15, KÖN Farb

Investigation of the dephasing of tunneling systems in glasses using two-pulse polarisation echo experiments — •Masoomeh Bazrafshan, Paul Faßl, Martin Schwarze, Angela Halfar, Annina Luck, Andreas Fleischmann, and Christian Enss — Kirchhoff Institut für Physik, Universität Heidelberg

Low temperature properties of glasses are governed by atomic tunneling systems. Many aspects are well described within the phenomenological standard tunneling model. Tunneling systems couple to their local strain fields which gives rise to a strain-mediated coupling among them. These interactions cause time-dependent variations in the energy splittings of tunneling systems when their neighbors undergo thermal transitions. This is the basis of the spectral diffusion model, which describes the dephasing of tunneling systems at very low temperatures. Experimentally, this dephasing of tunneling systems can be studied by two-pulse polarisation echo experiments. We have performed such echo decay measurements with an improved setup allowing us to observe echoes at very long delay times where the echo has decayed five orders of magnitude from its original amplitude. We have analysed the time and temperature dependent results in the framework of spectral diffusion model, finding very good qualitative agreement for the echo decay, but clear shortcoming in terms of the temperature dependence.