2006 Fiscal Year Final Research Report Summary
Quantum phase transition of liquid helium in aerogel
| Project/Area Number |
16540312
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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 |
Condensed matter physics II
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| Research Institution | Kanazawa University |
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Principal Investigator |
MATSUMOTO Koichi Kanazawa University, Graduate school of natural science and technology, Associate Professor, 大学院自然科学研究科, 助教授 (10219496)
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| Co-Investigator(Kenkyū-buntansha) |
ABE Satoshi Kanazawa University, Graduate school of natural science and technology, Lecturer, 大学院自然科学研究科, 講師 (60251914)
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| Project Period (FY) |
2004 – 2006
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| Keywords | helium / superfluidity / ultrasound / aerogel / phase transition |
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| Research Abstract |
We have presented evidence for quantum phase transition (QPT) on superfluid phase transition of helium 3 in 98% aerogel in 1997. However, the details of the QPT are not known so far. We studied the QPT of helium in aerogel for both helium 3 and 4 using ultrasound technique.
1. helium 4 and aerogel system
QPT is reported for helium 4 in porous glass with small pore. We have studied superfluid transition of helium 4 in aerogel with porosity between 92 and 97 %. The transition was suppressed by aerogel. We have made the phase diagram for this system. However, QPT was not observed in aerogel. We have observed many interesting phenomena in this research. For example, anomalous sound attenuation was observed with 97 % porous aerogel around 1.7 K. This result suggested possibility of mode conversion between first, second sound in superfluid and aerogel sound mode in this composite system.
Solidification of helium in aerogel was studied. Sound transmission trough the solid-liquid interface has been observed. Our experiment shows the crystal growth is suppressed by silica strands of aerogel.
2. helium3 and aerogel system
A nuclear demagnetizing refrigerator has been constructed for this experiment. The sound cell has acoustic cavities with aerogel and bulk liquid for comparison. The signal with aerogel has been observed using longitudinal ultrasound at 6 MHz. Because of the trouble of refrigerator, only preliminary experimental data was obtained. The experiment is ongoing.
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