Electrodynamics of amorphous media at low temperatures

Abstract

Amorphous solids exhibit intrinsic, local structural transitions, which give rise to the well-known quantum-mechanical two-level systems at low temperatures. We explain the microscopic origin of the electric dipole moment of these two-level systems: the dipole emerges as a result of polarization fluctuations between near degenerate local configurations, which have nearly frozen in at the glass transition. An estimate of the dipole's magnitude, based on the random first-order transition theory, is obtained and is found to be consistent with experiment. The interaction between the dipoles is estimated and is shown to contribute significantly to the Grüneisen parameter anomaly in low T glasses. In completely amorphous media, the dipole moments are expected to be modest in size despite their collective origin. In partially crystalline materials, however, very large dipoles may arise, possibly explaining the findings of Bauer and Kador [J. Chem. Phys., 118, 9069 (2003)].

Acknowledgements

PGW was supported by the NSF grant CHE 0317017. VL and RJS gratefully acknowledge the NSF grant CHE 0306287 and the Donors of the Petroleum Research Fund of the American Chemical Society. We thank the anonymous referee and Dr A. Heuer for their suggestions. We are happy to dedicate this bagatelle to Bob Harris, whose elegant contributions are many, but more than scan the range from the electrodynamical properties of matter, parity, and tunnelling systems, all of which enter the question discussed here.

Notes

§Current address: Department of Chemistry, University of Houston, Houston, TX 77204-5003, USA.

Additional information

Notes on contributors

Vassiliy Lubchenko§

§Current address: Department of Chemistry, University of Houston, Houston, TX 77204-5003, USA.