Berlin 2008 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 4: Matter at Low Temperature: Materials

TT 4.2: Vortrag

Montag, 25. Februar 2008, 10:00–10:15, H 3010

Impact of nuclear spins on two-pulse polarization echos in Glycerol. — •Masoomeh Bazrafshan, Gudrun Fickenscher, Celine Rüdiger, Marek Bartkowiak, Kathrin Reinhold, Andreas Fleischmann, and Christian Enss — Kirchhoff-Institut Für Physik,Universität Heidelberg

A few years ago surprising magnetic field effects were found in the dielectric properties of non-magnetic glasses at very low temperatures. For instance our 2-pulse polarization echo measurements on partially deuterated glycerol show strong magnetic field dependecies. It has since been established that this effect can be attributed to the tunneling motion of groups of molecules that carry nuclear quadrupole moments, between two different configurations of almost equal energy. This magnetic field effect saturates at about 60mT, when the nuclear Zeeman energy becomes larger than the quadrupole splitting. However, detailed studies have shown that one component of these magnetic effects saturates already at about 10 times smaller field. We have shown that the origin of this effect is the interaction of nuclear magnetic dipole moments of the hydrogen atoms in glycerol. Both effects are visible in the magnetic field dependence of the echo amplitude and a quantum beating at zero field which we have studied systematically on a series of glycerol samples with different degrees of deuteration. Numerical calculations were performed and compared to the experimental observations which enables us to probe the microscopic nature of tunneling systems in amorphous glycerol.