Dresden 2006 – wissenschaftliches Programm

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TT: Tiefe Temperaturen

TT 6: Solids At Low Temperature: Amorphous and Tunnel Systems, Glasses, ...

TT 6.2: Vortrag

Montag, 27. März 2006, 11:00–11:15, HSZ 105

Investigating the microscopic nature of tunnelling processes in amorphous glycerol — •Masoomeh Bazrafshan¹, Marek Bartkowiak¹, Herbert Zimmermann², Andreas Fleischmann¹, and Christian Enss¹ — ¹a) Kichhoff-Institut fuer Physik, Universitaet Heidelberg, Germany — ²b) Max-Planck-Institut fuer medizinische Forschung, Heidelberg, Germany

At temperatures below a few kelvin the properties of amorphous solids are dominated by atomic tunnelling systems. Over the past few years it was shown that the unexpected magnetic field effects, observed in many non-magnetic multicomponent glasses, originate from a coupling of the tunnelling motion to nuclear quadrupole moments present in the system. In dielectric polarisation echo experiments a strong magnetic field dependence of the echo amplitude as well as a periodic modulation of the echo decay, the so-called quantum beating, can be observed. The frequency of the quantum beating corresponds to the energy splitting of the quadrupole levels.

In this work we present dielectric echo measurements on partially deuterated glycerol, a system wich allows to introduce nuclear quadrupoles at specific sites of the molecule. By comparison with numerical calculations of the transition amplitudes we are able to suggest possible microscopic scenarios for tunnelling processes in amorphous glycerol. We believe that this work will provide important input for the development of a microscopic theory of glasses.