Simultaneous Measurements of an Ultrasound and a Torsional Oscillator for 4He in a Nanoporous Glass

Author: Kobayashi Toshiaki   Taniguchi Junko   Suzuki Masaru   Shirahama Keiya  

Publisher: Springer Publishing Company

ISSN: 0022-2291

Source: Journal of Low Temperature Physics, Vol.148, Iss.5-6, 2007-09, pp. : 797-801

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Abstract

Previously, we carried out ultrasonic measurements for liquid 4He filled in a nanoporous glass (Gelsil), and observed an increase in the sound velocity due to decoupling of the superfluid component. At zero pressure, the superfluid transition temperature T C is suppressed to 1.4 K from the bulk lambda point, 2.17 K. This behavior is the same as torsional oscillator measurements by Yamamoto et al. (Phys. Rev. Lett. 93:075302, 2004). However, the pressure dependence of T C and the temperature dependence of the superfluid fraction are very different from the torsional oscillator measurements. In order to clarify the origin of the difference, we have developed a new technique of simultaneous measurement of an ultrasound and a torsional oscillator, and the system successfully works for a nanoporous glass. Here, we compare decoupling of the superfluid component for 4He films between an ultrasound and a torsional oscillator.

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