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Regensburg 2000 – scientific programme

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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

Wednesday, March 29, 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.

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