1999 Fiscal Year Final Research Report Summary
Study of Phase Transition of Superfluid Helium 3 in sub micrometer Space
| Project/Area Number |
10640352
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
固体物性Ⅱ(磁性・金属・低温)
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| Research Institution | OSAKA CITY UNIVERSITY |
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Principal Investigator |
ISHIKAWA Osamu Osaka City University, Graduate School of Science, Associate Professor, 理学部, 助教授 (90184473)
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| Co-Investigator(Kenkyū-buntansha) |
MATSUBARA Akira Osaka City University, Graduate School of Science, Research Associate, 理学部, 助手 (00229519)
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| Project Period (FY) |
1998 – 1999
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| Keywords | Superfluid Helium 3 / Phase Transition / Anisotropic Superfluid / Slab Geometry / Coherence Length / Size Effect / Nuclear Magnetic Resonance / Thin Helium 4 layers |
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| Research Abstract |
It became clear that the boundary condition of ^3He quasi particles at the surface had a great effect on the stability of superfluid phases by our experimental study on superfluid ^3He in 0.8 μm slab geometry. The anisotropy of ^3He superfluid state appears in real space and this anisotropy competes with the anisotropy of sample cell. As a result it is expected that we can observe the particular phase transition between superfluid states (A-B phase transition) and the suppression of the superfluid transition temperature when we put liquid ^3He in a cell whose size is close to the coherence length. The coherence length varies depending on pressures, the lower pressure, the longer coherence length. From this point of view the above expectation becomes more obvious at lower pressures.
In our study, we developed the high Q-value tuned circuit for NMR detection with the low temperature amplifier to get the enough S/N ratio. We observed the lower A-B phase transition temperatures than those in 1.1 μm slab geometry at all pressures and also observed the large suppression of superfluid transition temperature. These were enhanced at lower pressures as expected and no A-B transition occurred lower than about 2 bar. The critical thickness well explained A-B phase transition phenomena at both slab geometries. Surprisingly the A-B phase transition temperature became higher when we put a few ^4He layers on the boundary surface. The superfluidity of thin ^4He layer seems to change the boundary condition for ^3He quasi particle and to lift A-B transition temperature. All the theoretical arguments, however, showed the opposite result so far. We need new theoretical work to discuss about our results.
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