Study of nonlocal correlation of Cooper-pair tunnelings in systems of small Josephson junctions

2014 Fiscal Year Final Research Report

• Project/Area Number: 24340067
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Partial Multi-year Fund
• Section: 一般
• Research Field: Condensed matter physics I
• Research Institution: The University of Electro-Communications
• Principal Investigator: SHIMADA Hiroshi 電気通信大学, 情報理工学(系)研究科, 准教授 (60216067)
• Co-Investigator(Renkei-kenkyūsha): MIZUGAKI Yoshinao 電気通信大学, 情報理工学研究科, 教授 (30280887)
• Project Period (FY): 2012-04-01 – 2015-03-31
• Keywords: 微小ジョセフソン接合 / 電流ドラッグ / 電流ミラー / 非局所相関 / ブロッホ振動 / JQPサイクル

Outline of Final Research Achievements

We have experimentally shown that application of high-frequency radiation in a range 100 kHz-170 GHz to an array of small Josephson junctions weaken its Coulomb blockade of Cooper-pair tunneling and induce conductance in the array. There exists a correlation between currents in two arrays of small Josephson junctions separated by a distance of the order of 10 um. We have demonstrated that this can be understood quantitatively if we assume that a current in one array induces an ac voltage in the other array the magnitude of which is proportional to the square root of the current in the first. We have also investigated I-V characteristics of an array of small junctions connected to SQUID arrays which serve as its environmental impedance. We showed a clear Bloch oscillation when the environmental impedance was large as well as current plateaus superposed. The latter has turned out due to a kind of nonlocal interaction of the tunnelings in the SQUID arrays and those in the junction array.

Free Research Field

低温物性