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TT: Tiefe Temperaturen

TT 23: Posters Superconductivity, Solids at Low Temperature

TT 23.60: Poster

Montag, 7. März 2005, 14:00–18:00, Poster TU D

Magnetic field dependence of polarisation echos generated in mixtures of amorphous glycerin and heavy water — •C. Fischer, M. Bartkowiak, S. Hunklinger, and C. Enss — Kichhoffinstitut für Physik, Universität Heidelberg, Germany

The properties of glasses at temperatures below a few kelvin are dominated by atomic tunneling systems. Measuring dielectric polarization echos are one way to gain a better understanding of these energetically low-lying excitations.

In this work we present measurements on glassy mixtures of glycerin and heavy water as well as on deuterated glycerin. We observed oscillations superimposed on the decay of spontaneous echos, the so-called quantum beating, as well as the alteration of the integrated echo amplitude by the application of an external magnetic field.

Both effects originate from the introduction of nuclear quadrupole moments to the amorphous system, they are a direct consequence of the deuteration. The beating frequencies measured were in good agreement with quadrupole frequencies determined in NMR experiments.

Having a technique sensitive to tunneling systems with nuclear quadrupoles only, we can use selective isotopic substitution as a marker method. This opens a new way to microscopic studies of the tunneling systems.