2004 Fiscal Year Final Research Report Summary
Theoretical study on vortex states in superconductors
| Project/Area Number |
13640341
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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 | Hokkaido University |
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Principal Investigator |
KITA Takafumi Hokkaido Univ., Grad.School of Science, Asso.Prof., 大学院・理学研究科, 助教授 (20186224)
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| Project Period (FY) |
2001 – 2004
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| Keywords | Type-II superconductors / Quantized vortices / Superfluid ^3He / Bose-Einstein condensation / Upper critical field |
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| Research Abstract |
Theory of the de Haas-van Alphen effect in type-II superconductors
We performed numerical and analytical studies of the de Haas-van Alphen oscillation in type-II superconductors. We derived an analytic formula for the extra attenuation observed in the vortex state, which can also be used to estimate the band and/or angle dependent gap anisotropy. Using it, we estimated gap amplitude of several materials.
Vortex structures of superfluid ^3He and spinor Base-Einstein condensates
Based on the Ginzburg-Landau equations near the transition temperature, we performed a theoretical study on the vortex-lattice structures of superfluid ^3He in rapid rotation to present an entire phase diagram. We also predicted novel vortex structures of the three-component spinor Bose-Einstein condensate.
Calculation of the Maki parameter
The Maki parameter is one of the most basic quantities in type-II superconductors which is relevant to the specific-heat jump at the transition, the change in the slope of the magn
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etization curve at the transition, etc. We performed a detailed study on it to show that it has a strong dependent on the detailed Fermi-surface structures, especially in dean materials.
Calculation of the upper critical field of type-II superconductors
The upper critical field H_<c2> is one of the most basic quantities in type-II superconductors. It has been knownn for a long time that H_<c2> of clean samples depends on the detailed Fermi-surface structures. However, few detailed calculations have been performed yet. We derived an H_<c2> equation which enables us to calculate H_<c2> quantitatively by using Fermi surfaces from first-principles electronic-structure calculations. Using it, we performed detailed studies on H_<c2> of Nb, NbSe_2, and MgB_2 to find excellent quantitative agreements with experiments.
Calculation of the flux-flow resistivity of type-II superconductors near H_<c2>
The electronic resistance in the vortex state of type-II superconductors is a complicated phenomenon involving the motion of vortices which has not been understood sufficiently. We performed a detailed calculation on this flux-flow resistivity near the upper critical field to clarify the overall temperature and impurity-concentration dependences. Less
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