2006 Fiscal Year Final Research Report Summary
Study of Novel Quantum Phenomena in Helium Confined in Nano-Structures
| Project/Area Number |
16204028
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| Research Category |
Grant-in-Aid for Scientific Research (A)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Condensed matter physics II
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| Research Institution | Keio University |
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Principal Investigator |
SHIRAHAMA Keiya Keio University, Science and Tech., Associate Professor (70251486)
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| Co-Investigator(Kenkyū-buntansha) |
SUZUKI Masaru Keio University, Electro-Communications, Professor (20196869)
SHIBAYAMA Yoshiyuki Keio University, Science and Tech., Associate Professor (20327688)
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| Project Period (FY) |
2004 – 2006
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| Keywords | Helium / Superfluidity / Quantum Phase Transition / Bose System / Quantum Fluid / Quantum Solid / Supersolid / Nanoporous Material |
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| Research Abstract |
This research project was planned to study and search for various novel quantum phenomena in helium (^4He) confined in nanoporous structures. The project involves mainly five subjects. The outcome are as follows:
1. ^4He in nano-porous glass : (A) The liquid-solid phase boundary was determined by isochoric pressure measurements. We have discovered a peak in heat capacity of confined ^4He at much higher temperatures than the superfluid transition temperature. The heat capacity peak definitely shows the formation of localized Bose-Einstein condensates in nanopores. (B) We developed a new simultaneous measurement technique of torsional oscillator and ultrasound. By this technique we have found that the superfluid transition temperature is independent of frequency, but has a strong porous sample dependence. (C) We have succeeded to control the pore size of the nanoporous glass by preplating a few atomic layers of Krypton atoms. The superfluid transition temperature decreases after preplatin
… More
g, indicating that the decrease of the effective pore size suppress superfluidity.
2. Search for quantum effects in hydrogen (H_2) in nanoporous glasses : Aiming at searching for BEC and superfluidity in molecular hydrogen, we have studied the pore size dependence of supercooling of liquid H_2 by isochoric pressure measurements. We have found that the majority of supercooled H_2 solidify at around 9 K. However, a small amount of H_2, probably confined in narrowest pores, remains liquid down to about 7 K in 2.5-nm porous glass. This indicates that BEC can be observed by confining H_2 in uniform pores narrower than 2.5 nm.
3. Superfluidity of ^4He in one-dimensional nanopores: Torsional oscillator studies for ^4He in 1D nanopores in FSM-16 revealed that superfluidity is dramatically suppressed by pressurizing liquid, with Tc reaching 0 K at around 2 Mpa. This is second example of quantum superfluid transition of confined ^4He.
4. ^4He in regular 3D pore structure : Torsional oscillator and pressure experiments are underway.
5. Supersolid studies of ^4He : We have conducted torsional oscillator experiments for bulk solid ^4He and solid in nano porous glasses. The former study revealed strong dependence of supersolid behaviors on sample history. Less
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[Journal Article] Comparison between torsional oscillator and ultrasonic measurements of liquid ^4He confined in nano porous media2007
Author(s)
J., Taniguchi, H., Ichida, Y., Aoki, S., Fukazawa, M., Hieda, M., Suzuki
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Journal Title
Journal of Low Temperature Physics Vol. 148
Pages: 791-795
Description
「研究成果報告書概要(欧文)」より
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[Journal Article] Ultrasonic study for superfluidity of ^4He filled in a nanoporous glass2006
Author(s)
T., Kobayashi, S., Fukazawa, J., Taniguchi, M., Suzuki, K., Shirahama
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Journal Title
Proceedings of the 24th International Conference on Low Temperature Physics (LT24), AIP Conference Proceedings Series Vol. 850
Pages: 277-278
Description
「研究成果報告書概要(欧文)」より
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[Journal Article] Search for superfluidity of solid ^4He in a porous Vycor glass by means of the ultrasound technique2006
Author(s)
T., Kobayashi, S., Fukazawa, J., Taniguchi, M., Suzuki, K., Shirahama
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Journal Title
Proceedings of the 24th International Conference on Low Temperature Physics (LT24), AIP Conference Proceedings Series Vol. 850
Pages: 333-334
Description
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