Regensburg 2000 – wissenschaftliches Programm

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TT: Tiefe Temperaturen

TT 17: Postersitzung II: Pinning und Vortexdynamik (1-8), Supraleitung: Theorie (9-13), Korrelierte Elektronen (14-48), Niederdimensionale Systeme (49-68), Quantenflüssigkeiten (69-75)

TT 17.72: Poster

Mittwoch, 29. März 2000, 14:30–18:00, A

Ultrasonic investigations of ³He in 97.2% aerogel — •L. Hristakos, E. Nazaretski, K. Taubenreuther, H. Goetz, and G. Eska — Physikalisches Institut Universitaet Bayreuth, D-95440 Bayreuth

Transmission and surface impedance measurements were performed on ³He in 97.2% aerogel. The ³He samples (20 mm³) (one was filled with the aerogel and one served as a “bulk” reference ³He) were enclosed in between the transmitter and receiver quartzes (diameter 3mm, distance between quartzes 3mm, frequency 10MHz). The quartzes were operated in a pulsed technique.
In order to seperate sound excitation of the aerogel strands from those in ³He, we investigated gaseous ³He (0.4 bar at 300K) at temperatures from 300 K down to 0.6 mK where a ³He film covers the aerogel.
No transmission was observed in “bulk” ³He above 80 K. However, in aerogel transmission was evident even at room temperature. In addition we observed an increase in the intensity of the transmission signal at around 1 mK for both the bulk as well as the aerogel sample. This increase was not present in the surface impedance measurements, but, in these measurements an anomaly was found at around 5 mK. This anomaly was quite similar for both samples.
We also performed experiments on fluid ³He at 20 bar. A preliminary analysis of the data shows the expected behaviour for the bulk sample in the first and zero sound regime. In the aerogel sample however a deviation from the fermi-liquid behaviour was found.