Low-frequency elastic properties of glasses at low temperatures [Elektronische Ressource] : investigations with double-paddle oscillators based on a dc-SQUID readout / presented by Xuewei Cao

Dissertationsubmitted to theCombined Faculties for the Natural Sciences and for Mathematicsof Ruperto-Carola-University of Heidelberg, Germanyfor the degree ofDoctor of Natural Sciencespresented byM.-Sc. Xuewei Caoborn in : Tianjin, P. R. CHINAOral examination: Dec 7, 2004Low-frequency elastic propertiesof glasses at low temperaturesInvestigations with double-paddle oscillatorsbased on a dc-SQUID readoutReferees: Prof. Dr. Siegfried HunklingerProf. Dr. Heinz HornerWithin this thesis low frequency measurements on the elastic properties ofamorphous solids (a-SiO and BK7) at low temperatures using mechanical2oscillators were carried out. A main aspect was to develop a novel detectiontechnique for double-paddle oscillators within the environment of a dilution re-frigerator. The inductive detection mechanism is based on the high sensitivityof a commercial dc-SQUID. The superiority of the new technique compared tothe conventional capacitive detection method was demonstrated in measure-ments on di eren t glass samples. The resolution was improved more than oneorder of magnitude already in these rst experiments. Using the new tech-nique, the relative change of sound velocity and the internal friction of a-SiO2and BK7 were investigated in the temperature range form 5mK to about 1Kfor several frequencies. The results agree favourably with former measurementson a-SiO detected by the capacitive readout.