Berlin 2012 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 12: Glasses II (joint session with DY)
CPP 12.9: Vortrag
Dienstag, 27. März 2012, 12:00–12:15, MA 004
Probing Spectral Diffusion Theory in Glasses Through Polarization Echo Measurements — •Gudrun Fickenscher, Christian Schötz, Paul Faßl, Masoomeh Bazrafshan, Manfred von Schickfus, Andreas Fleischmann, and Christian Enss — Kirchhoff Institute, Heidelberg University, Germany
Many low temperature properties of glasses can be well described by the standard tunnelling model. It assumes an ensemble of isolated tunnelling systems (TS) with a broad distribution in energy splitting and asymmetry. They can couple resonantly to electric fields and can therefore be probed by polarization echo measurements. When looking at dynamic properties of glasses, however, the influence of the TSs in the surrounding of the resonantly probed TSs has to be taken into account. Spectral diffusion theory* assumes that transitions in thermally excited TSs change the local fields at the positions of the resonant TSs, thus changing their energy splitting and phase. This affects the decay behaviour of the polarization echo amplitude with respect to the delay time.
We have performed different types of polarization echo measurements including 2-pulse echoes which show an almost pure T2 decay and 3-pulse echoes which are more sensitive to T1 processes. The setup allows for measurements with very long delay times of several milliseconds. We calculated the decay in echo amplitude within the framework of the spectral diffusion theory and compared the results.
* J.L. Black, B.I. Halperin, Phys. Rev. B 16 (1977), 2879.