2005 Fiscal Year Final Research Report Summary
Studies on Superconducting States of Unconventional Superconductors using Local-Field Measuring Techniques
| Project/Area Number |
14204034
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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 |
固体物性Ⅱ(磁性・金属・低温)
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| Research Institution | The University of Tokyo |
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Principal Investigator |
TAMEGAI Tsuyoshi The University of Tokyo, School of Engineering, Associate Professor, 大学院工学系研究科, 助教授 (30183073)
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| Co-Investigator(Kenkyū-buntansha) |
TOKUNAGA Masashi The University of Tokyo, School of Engineering, Research Associate, 大学院工学系研究科, 助手 (50300885)
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| Project Period (FY) |
2002 – 2005
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| Keywords | magneto-optical imaging / Hall probe magnetometry / crossing-lattices state / triplet superconductor / inhomogeneity |
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| Research Abstract |
By using local-field measuring technique, such as magneto-optical imaging and micro-Hall probe magnetometry, we have clarified the detailed magnetic properties of various novel states in unconventional superconductors.
In highly anisotropic layered superconductor Bi2Sr2CaCu2O8+y, a novel vortex state with coexisting two kinds of vortices are realized under tilted fields. Pancake vortices and Josephson vortices are generated by the field components perpendicular and parallel to the superonducting plane. As a function of two-field components, various ground states of vortex systems are realized. The characteristic vortex arrangements of these states are 'vortex chains', where pancake vortices are decorating Josephson vortices by weak attractive interaction between them. This interaction can also be utilized to control the pancake vortices using Josephson vortices. We have demonstrated such controllability by visualizing the distribution of pancake vortices. In particular, vortex lens effe
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ct, where pancake vortices are focused at the center of the sample by the help of Josephson vortices have been demonstrated for the first time.
A layered intermetallic superconductor CaAlSi with AIB2 structure shows an anomalous angular dependence of the upper critical field. By contrast, in a related compound CaGaSi, the upper critical field normally. By visualizing vortex penetration on the ac plane of CaAlSi, exsistence of inhomogeneity along c-axis is clarified. Ga-doping gradually suppresses such an anomalous vortex penetration.
PrOs4Sb12 is claimed to be a triplet superconductor with broken time-reversal symmetry. In order to reveal anomalies related to this novel superconducting state, we have performed detailed local field measurements using micro-Hall proves. It is found that the local field shows an anomaly when the local magnetic induction changes the sign, similar to the case of another triplet superconductor Sr2Ru04. We now tentatively ascribe such anomalies to the presence of domain boundaries between domains with opposite chiralities. Less
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