Regensburg 2007 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 4: Solids at Low Temperature - Materials
TT 4.4: Vortrag
Montag, 26. März 2007, 12:15–12:30, H18
Effects of Nuclear Spins in Amorphous Glycerol on the Amplitude of Dielectric Polarization Echoes — •Masoomeh Bazrafshan1, Gudrun Fickenscher1, Kathrin Reinhold1, Marek Bartkowiak2, Herbert Zimmermann3, Andreas Fleischmann1, and Christian Enss1 — 1Kirchhoff-Institut für Physik, Universität Heidelberg — 2Forschungszentrum Rossendorf, Dresden — 3Max-Planck-Institut für Medizinische Forschung, Heidelberg
The properties of amorphous solids below a few Kelvin are determined by tunnelling systems. It has been shown that coupling of nuclear quadrupole moments to the tunnelling motion leads to magnetic field effects in non-magnetic glasses. We find that, in smaller B-fields, the presence of nuclear magnetic dipole moments interacting with each other by the magnetic dipole-dipole interaction results in similar magnetic field effects.
Both effects have been studied systematically with dielectric two-pulse polarization echoes on a series of partially deuterated glycerol samples. Decay measurements at very low temperatures show quantum beating with two different groups of frequencies, which can be attributed to the quadrupole energy splittings (~130kHz) and the dipole-dipole splittings (~30kHz). In addition, the beating amplitudes feature an unexpected temperature-dependent damping.
We present the measured data and compare the results with detailed numerical simulations. On this basis we draw possible conclusions about the microscopic nature of tunnelling systems in amorphous glycerol.