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SYEL: Symposium Energy Landscapes: Statistical Physics of (Spin-)Glasses, Biomolecules, Clusters and Optimization Problems

SYEL 1: Energy Landscapes: Statistical Physics of (Spin-)Glasses, Biomolecules, Clusters and Optimization Problems (SYEL)

SYEL 1.3: Hauptvortrag

Montag, 22. März 2010, 11:00–11:30, H1

Nuclear Spins Reveal the Microscopic Nature of Tunneling Systems in Glasses — •Christian Enss — Kirchhoff-Institut für Physik, Universität Heidelberg, INF 227, 69120 Heidelberg

The low temperature properties of disordered solids, like glasses or crystals with certain substitutional defects are governed by atomic tunneling systems. Until recently it was believed that the dielectric properties of insulating materials devoid of magnetic impurities should not or only very weakly depend on external magnetic fields. Experiments on glasses show in contrast to that a strong magnetic field dependence of the dielectric susceptibility of such materials at ultralow temperatures. We will discuss polarization echo experiments that proof that these effects are caused by tunnelling particles with nuclear magnetic moments. Using isotope substitution we demonstrate the role of nuclear quadrupole and nuclear magnetic dipole moments regarding the magnetic field dependence. We also show that tunnelling particles with nuclear moments can be used as local probes to investigate the microscopic nature of tunnelling systems.