1999 Fiscal Year Final Research Report Summary
Ballistic Electron Transport Characteristics in Ultrahigh-Purity Metal Single Crystals
| Project/Area Number |
10640350
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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 | Hiroshima University |
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Principal Investigator |
HASHIMOTO Eiji Hiroshima University, Hiroshima Synchrotron Radiation Center, Associate Professor, 放射光科学研究センター, 助教授 (50033907)
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| Co-Investigator(Kenkyū-buntansha) |
UEDA Yoshitake Hiroshima International University, Faculty of Health Sciences, Associate Professor, 保健医療学部, 助教授 (80106799)
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| Project Period (FY) |
1998 – 1999
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| Keywords | ballistic electron transport / electron mean free path / electrical conductivity / electronic transport / anisotropy / aluminum / ultrahigh-purity metal |
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| Research Abstract |
To understand the nature of the electrical conductivity in the quantum limit, measurements have been made at 4.2 K on the electronic conduction in single crystals of ultrahigh-purity aluminum with RRR ( ≡ RィイD2300KィエD2/RィイD24.2KィエD2) of more than 150000. In this material, the mean free path of a conduction electron reaches about 5 mm at low temperatures. Main results are summarized as follows.
(1) Orientation Dependence of Negative Bend resistance
Negative bend resistance, an effect of the ballistic conduction of electrons, was observed in cross-shaped specimens with the (001) main surface. This effect is weakened as an electron-shot shifts from <110> to <100> , showing a strong correlation with the structure of the Fermi surface. In the <100> direction, the second-zone Fermi surface is nearest to the zone boundary.
(2) Anisotropy of the Bulk Residual Resistivity ρィイD2bィエD2
Accepted wisdom tells us that there should be no anisotropy of resistivity in a cubic metal like aluminum. However, in the region of ultrahigh purities, we identified anisotropy of ρィイD2bィエD2: ρィイD2bィエD2 increases in the order of the [110], [111] and [001] current directions. This anisotropic behavior is consistent with the orientation dependence of the ballistic electron transport characteristics described in (1). The ρィイD2bィエD2 value along [001] is about twice as large as that along [110].
(3) Nonlinear I- V Characteristics
When the electron mean free path is enlarged. Ohm's law, j =σ・E, does not hold for any portion of the specimen under the action of a nonuniform electric field. This means that the deviation from equilibrium of the electron distribution can nolonger be regarded as being a first order infinitesimal : the electron distribution function does not always remain its cubic symmetry even though the applied electric field is small. This confirms the anisotropy of ρィイD2bィエD2 above.
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