| Project/Area Number |
09640419
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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 | THE UNIVERSITY OF TOKYO |
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Principal Investigator |
YAGI Ryuta THE UNIVERSITY OF TOKYO,GRADUATE SCHOOL OF SCIENCE,RESEARCH ASSOCIATE, 大学院・理学系研究科, 助手 (60251401)
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| Project Period (FY) |
1997 – 1998
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| Project Status |
Completed (Fiscal Year 1998)
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| Budget Amount *help |
¥3,200,000 (Direct Cost: ¥3,200,000)
Fiscal Year 1998: ¥700,000 (Direct Cost: ¥700,000)
Fiscal Year 1997: ¥2,500,000 (Direct Cost: ¥2,500,000)
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| Keywords | MQT / Energy Dissipation / Shunt Resistor / Tunneling Resistor / S-I Transition / エネルギー散逸 / 単一電子トランジスタ / 走査顕微鏡 |
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| Research Abstract |
We studied the effect of energy dissipation on macroscopic quantum tunneling (MQT) in single small Josephson junction. We succeeded in observing dissipative phase transition. Energy dissipation was tuned by attaching a resistor at the very vicinity of small Josephson junction. Here we kept the normal state tunneling resistance of Josephson larger than the quantum resistance, and varied the resistance of the attached resistor. In case of Ohmic shunt resistor made of nickel chromium alloy, the Josephson junction that exhibits insulating behavor recovers superconductivity when the shunt resistance Rs was less than the quantum resistance Rq=h/4e2. On the other hand, when Rs > Rq, it was insulating. We determined the phase diagram for superconductor-insulator transition by varying EJ/EC values. The case of tunneling resistance was also studied. A normal small tunneling junction was connected to a small Josephson junction in parallel. The ohmic shunt resistor and the tunneling junction have different types of energy dissipation in that the charge transfer in the former case is continuous while in the latter discrete. In a theoretical prediction, the phase diagrams for the S-I transition are different between these two. In preliminary experiments, the tunneling junction acted quite similarly to the ohmic shunt resistance.
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