Hamburg 2001 – wissenschaftliches Programm
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TT: Tiefe Temperaturen
TT 6: Postersitzung I: Josephsonkontakte und SQUIDs, Supraleitung: Theorie, Korrelierte Elektronen, Niederdimensionale Systeme, Magnetotransport, Quantenhalleffekt, Kohlenstoff-Nanoröhrchen, Quantenflüssigkeiten
TT 6.72: Poster
Montag, 26. März 2001, 14:30–17:00, Rang S\ 3
Ultrasonic investigations of 3He in 97% aerogel below the superfluid transition of 3He — •L. Hristakos, H.Götz and G.Eska — Physikalisches Institut, Universität Bayreuth, D-95440 Bayreuth
A series of pulsed sound measurements were performed in order to study sound propagation (10 MHz) through aerogel (of 97% porosity) filled with 3He. The pressure inside the cell was varried from 0-29 bar and the temperature from 0.5-200 mK. Two samples were measured simultaneously, one filled with the system 3He-aerogel , the other filled with bulk-3He which served as the reference sample. The transmission of sound through 3He-aerogel was different from that through bulk-3He at all temperatures and pressures. A supression of Tc of approximately 0.2 mK was observed. This supression of Tc appears to be only slightly dependent on p ressure. Furthermore the transmitted signal in the 3He-aerogel volume was smaller by a factor of 20 compared to that in bulk-3He. In superfluid bulk-3He the amplitude of the transmitted signal increased by a factor of 2 from Tc to 0.5Tc, whereas the corresponding change in the 3He-aerogel system for the same temperature variation was only an increase of 1.05. The curvature of the temperature dependence of this signal increase in the 3He-aerogel system was also very different from that in bulk-3He. In the temperature range 0.5Tc-Tc no indication of a collective mode was detected.