Berlin 2008 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 7: Matter at Low Temperature: Poster Session

TT 7.6: Poster

Montag, 25. Februar 2008, 14:00–18:00, Poster B

New information on the microscopics of tunneling systems from mixtures of glycerol and deuterated glycerol. — •Celine Rüdiger, Masoomeh Bazrafshan, Gudrun Fickenscher, Andreas Fleischmann, and Christian Enss — Kirchhoff-Institut Für Physik,Universität Heidelberg

The properties of amorphous materials at temperatures below 1K are genrally described by localized groups of atoms or molecules, cooperatively moving between two configurations with comparable energy (Tunneling Systems).However, barely anything is known about the microscopic nature of these TS. Recently we have shown, that the microscopic nature of TS can be probed by the 2-pulse polarisation echo experiments, since the coupling of nuclear electric qudrupole moment to the tunneling motion leads to a quantum beating of the echo amplitude, as well as a dependence of the echo amplitude on magnetic field. Our investigations on partially deuterated amorphous glycerol revealed that the tunneling motion has a rotational component. The observed effects can e.g. be described by the rotation of one molecule by an average angle of 15°. However, also the assumption of a coherent tunneling of a large group of molecules by a fraction of this angle would explain the observed behavior. We started a series of measurements on mixtures of glycerol and partially deuterated glycerol in order to study the cooperative nature of TS and determine the average number of molecules that are involved in a TS as well as the typical angle by which they rotate. We show the first experimental results and discuss microscopic models that are able to describe the observed behavior.