1997 Fiscal Year Final Research Report Summary
Establishment of the Reproducibility of the Superconducting Gap in Tunneling measurements.
| Project/Area Number |
08640436
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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 | Tohoku University |
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Principal Investigator |
KUNII Satoru Tohoku Univ., Dept.of Physics, Associate Professor, 大学院・理学研究科, 助教授 (10004368)
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| Project Period (FY) |
1996 – 1997
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| Keywords | Superconductor / Superconducting-gap / Tunneling effect / Point-contact |
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| Research Abstract |
The purpose of this research project is to establish the reproducibility of superconducting gap value in the point-contact tunneling spectroscopy. In the superconductor the Andreev-reflection changes depend on the contact size (correlated to the phase coherence) so as to arise the excess current and the subharmonic gap structure. In this study it is tried to change the contact size and to cancel the vector-unbalance with the phase of the detected signal. For this aim the two-phase output oscillator is used to remove the circuit unbalane voltage and the unbalance signal phase. The equipment for the point-contact tunneling measurements was constructed to prevent the contamination and the needle-pressure by the automatic in situ cleaning method developed by us. The superconductor single crystal YB_6 was grown by a vertical floating zone method by an author. The measurements were performed to get the differential resistivity as a function of the bias-voltage at very low temperature. It is possible to change the phase of 0.1 degree in the two phase output oscillator independently. The precise variable resistor was used to get voltage-balance so far instead of the two phase output oscillator. Therefore it was difficult to control the phase relation in the circuit so as to arise the non-reproducible signal or the ghost signal. By this research project the unbalance of the voltage and the phase are removed simultaneously, so that the distinction between the signal from the sample and the signal from the circuit is achieved.
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