| Project/Area Number |
17560293
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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 |
Electronic materials/Electric materials
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| Research Institution | TOKAI UNIVERSITY |
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Principal Investigator |
INUSHIMA Takashi Tokai University, School of Information Science and Technology, Professor, 情報理工学部, 教授 (20266381)
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| Project Period (FY) |
2005 – 2006
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| Project Status |
Completed (Fiscal Year 2006)
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| Budget Amount *help |
¥3,500,000 (Direct Cost: ¥3,500,000)
Fiscal Year 2006: ¥1,600,000 (Direct Cost: ¥1,600,000)
Fiscal Year 2005: ¥1,900,000 (Direct Cost: ¥1,900,000)
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| Keywords | Superconductivity of InN / Fermi surface / Electron Localization / Critical current / モット転移濃度 |
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| Research Abstract |
Temperature dependence of the resistivity of InN was investigated as a function of carrier density. The carrier density was changed from n_e=1.8x10^<18>cm^<-3> to 1.5x10^<19>cm^<-3> by Si doping. The InN investigated showed metallic conduction above 20 K. At lower temperatures there was a resistivity anomaly originating from carrier localization in the a-b plane, which was confirmed by the magnetoresistance at 0.5 K. The Shubnikov de-Haas oscillation showed that InN had a spherical Fermi surface and its radius increased according to the increase of ne when n_e<5x10^<18>cm^<-3>. In addition an oscillation corresponding to the constant carrier density of 4.5x10^<12>cm^<-2> was observed in the field applied perpendicular to the a-b plane. This oscillation showed an anomalous angle dependence on the magnetic field. Taking into account this density, we determined the critical carrier density of the Mott transition to be 2x10^<17>cm^<-3>. Anisotropy of localization was observed within the a-b plane, which indicates that the distribution of the electrons was not uniform in the a-b plane. From these results, an electronic structure at the fundamental absorption edge of InN grown on sapphire (0001) was presented.
On the other hand, samples with carrier densities n_e as low as 4x10^<17>cm^<-3> show superconductivity with T_c= 0.47 K (midpoint). As in the layered cuprate high Tc superconductors, the vortex solid of InN is melted by thermal fluctuation and by the external magnetic field. The field dependence of the critical current J_c exhibits an exponential decay over a wide range of magnetic field, which is ascribed to the current tunneling through micro Josephson-junctions. We propose a mechanism where the anisotropy of J_c is related to the presence of In-In chains of finite length in the ab plane.
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