| Budget Amount *help |
¥2,400,000 (Direct Cost: ¥2,400,000)
Fiscal Year 2006: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 2005: ¥700,000 (Direct Cost: ¥700,000)
Fiscal Year 2004: ¥1,200,000 (Direct Cost: ¥1,200,000)
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| Research Abstract |
In this research, we have studied both theoretically and experimentally the fluctuation conductivity o' analysis in high-Tc superconductors from a viewpoint of the short-wavelength fluctuation (SWF).
1. Theoretical aspects : We have extended existing theories of o' to the cases of high-Tc superconductors with intrinsic properties. (1-1) In-plane o' of Aslamazov-Larkin (AL) term, anomalous Maki-Thompson (MT) term and the 3^<rd> term including regular MT and density-of-state terms is extended to the case of SWF. (1-2) The same approach is applied to out-of-plane o' for each term. (1-3) Also considered in SWF regime are effects of two to three dimensionality and effects of two-band character.
2. Experimental aspects : Above-obtained expressions have been adopted to analyze experiments on the following systems (2-1) Films and polycrystalline systems of YBa_2Cu_3O_<7-y> with impurities. (2-2) Polycrystalline LaBaCaCu_3O_<7-δ>. (2-3) Polycrystalline (Bi, Pb)_2Sr_2Ca_2Cu_3O_y. (2-4) Bi_2Sr_2(Ca
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_<1-x>Y_x)Cu_2O_<8+δ> single crystals. Theory (1-1) has been employed to o' analyses in (2-1〜2-4) systems, finding excellent fits to o' data, from which we can estimate various parameters which include conduction dimensionality, fluctuation amplitude C_F, anisotropic parameter r, cutoff parameter α, scattering lifetime τ, phase-coherent time τ_φ, and pair-braking parameter δ.
3. Results for analyses : Among these parameters, r, a and τ_φ are common factors that characterize properties of the systems especially from a viewpoint of sample quality. Other theoretical studies (1-2,1-3) have been applied to experimental data reported by others. Most of analyses have provided satisfactory descriptions on experiments, which allows us finding parameters that could be important to characterize each superconducting system, such as in-plane and out-of-plane coherence lengths and interband coupling strength. Most of our analyses support the existence of the MT term, and hence at least only a d-wave nature is not entirely responsible for a mechanism of superconductivity. In conclusion, we are of the opinion that our method of o' analyses gain important insights into superconducting properties, providing a new spectroscopic study of superconductivity. Less
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