Phenomenological Description of Conduction Mechanism of High-Tc Superconductors by Three-Fluid Model

Yoshio KOBAYASHI  Tadashi IMAI  

IEICE TRANSACTIONS on Electronics   Vol.E74-C   No.7   pp.1986-1992
Publication Date: 1991/07/25
Online ISSN: 
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Issue on Low Temperature Electronics)

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A new conduction mechanism of high-Tc superconductors is proposed to interpret experimental results phenomenologically, which will be called a three-fluid model, since nonpairing residual normal electron density nres is added into the super electron density ns and the normal electron density nn for a well-known two-fluid model. According to this model, an admittance equivalent circuit of superconductor in unit cube is derived and nn, ns, the complex conductivity , the surface impedance Zs, the skin depth δ, and the penetration depth λ are expressed as a function of temperature. Also such electron densities as ns, nn, and nres are expressed as a function of Zs. For Zs, , δ, λ, nn, and ns of a YBCO plate, the values calculated by this model agree well in the range T0.9 Tc with the ones measured by the dielectric resonator method, where Tc is the critical temperature; thus the validity of this model is verified. Also the ratio nres/nt0.18 is determined by using nres1.71024 m-3 and nt9.51024 m-3 obtained from the measured Zs values; thus it means that there is 18% nonpairing electron density in this YBCO plate. The ratio nres/nt can be used as figure of merit of high-Tc superconductors.