| Project/Area Number |
13450119
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Electronic materials/Electric materials
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| Research Institution | Utsunomiya University |
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Principal Investigator |
OYA Gin-ichiro Utsunomiya Univ., Dept.of Electrical and Electronic Eng., Professor, 工学部, 教授 (00006280)
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| Co-Investigator(Kenkyū-buntansha) |
HAMASAKI Katsuyoshi Nagaoka Univ.of Technology, Dept.of Electrical Eng., Professor, 工学部, 教授 (40143820)
KITAMURA Michihide Utsunomiya Univ., Dept.Electr.Electron.Eng., Associate Professor, 工学部, 助教授 (90161497)
IRIE Akinobu Utsunomiya Univ., Dept.of Electrical and Electronic Eng., Associate Professor, 工学部, 助教授 (90241843)
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| Project Period (FY) |
2001 – 2003
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| Keywords | high-T_c oxide superconductor / (Bi_<1-x>Pb_x)_2Sr_2CaCu_2O_y / intrinsic Josephson junction / Josephson effect / quasiparticle tunneling / d-wave superconductor / Coulomb blockade / subgap structure |
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| Research Abstract |
The purpose of this study is to clarify the essential tunneling properties and further develop the mesoscopic phenomena of small-sized natural superlattices of intrinsic Josephson junctions with lateral dimensions decreased down to submicron in layered high-temperature (high-T_c) oxide superconductor (Bi_<1-x>Pb_x)_2Sr_2CaCu_2O_y (0【less than or equal】x【less than or equal】0.2) single crystals (with transition temperatures T_c of〜85K), which consist of the stacking of superconducting CuO_2 layers of 0.3nm thickness alternating with other semiconducting or insulating layers of 1.2nm thickness, with the Josephson coupling between every adjacent superconducting layers via nonmetallic layers, and also to get information for the application of the superlattices to electronic devices.
The obtained results are as follows :
1.A fabrication technology of a small-sized rectangular mesa shape of superlattice devices composed of intrinsic Josephson junctions with lateral dimensions decreased down to
… More
0.7×0.7μm^2 has been developed for the single crystals.
2.Clear superconducting gaps have been successfully observed on the current-voltage characteristics of the small-sized devices. The values of gaps Δ(4.2K) have been found to be 25-30meV, independent of x.
3.A theoretical model to explain the overall profile of the quasiparticle tunneling current-voltage characteristics, which shows the superconducting gap, has been established.
4.Fine subgap structures have also been observed on the quasiparticle branches of the current-voltage characteristics, independent of x, temperature and weak magnetic field. This has been interpreted to be due to an interaction between Raman-active optical phonons and ac Josephson oscillation in the intrinsic Josephson junction.
5.Critical current densities J_c at 4.2K have been observed to decrease controllably with decreasing the lateral dimensions to submicron and increasing the number of junctions in the small-sized devices of Bi_2Sr_2CaCu_2O_y. This may be considered to be due to the Coulomb blockade effect. However, the single Cooper-pair tunneling has not been clearly confirmed for the devices. Less
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