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Prog. Theor. Phys. Vol. 43 No. 4 (1970) pp. 907-916

Superconductivity in Transition Metals with Nonmagnetic Impurities

Takashi Kusakabe

Departmet of Physics, Tokyo University of Education, Tokyo

(Received September 19, 1969)

Abstract:

The two-band model proposed by Suhl, Matthias and Walker for the theory of superconductivity of pure transition metals is extended to the transition metals in the presence of nonmagnetic impurities. It is found that the theory of superconductivity in the two-band model is rather sensitive to the choice of the cutoffs of the pairing interactions, in contrast to our expectations in the one-band model. That is, if ω_ss = ω_dd = ω_sd ≡ω_D, T_c always decreases with increasing impurity concentration and has a complete isotope effect. Furthermore if ω_ss = ω_dd ≠ω_sd (ω_ss = ω_D), T_c always decreases of increases with the impurity concentration according to the case of |α| < 1 or α> 1, respectively, and does not necessarily have the complete isotope effect, where ω_ss, ω_dd and ω_sd are the cutoffs for interactions giving a pairing of s-s, d-d and s-d electrons and α is a certain constant given by the pairing interaction, the density of states and the cutoffs. Besides, if ω_ss = ω_dd ≠ω_sd (ω_ss = ω_D), V_ss V_dd < V²_sd and α> 1, there may exist the phase transition of some kind (maybe of first order) at a certain impurity concentration, where V_ss, V_dd and V_sd are the strength of the pairing interactions. Thus we note here that the choice of the cutoffs of the pairing interactions is physically important for the study of superconducting transition metals.

URL : http://ptp.ipap.jp/link?PTP/43/907/
DOI : 10.1143/PTP.43.907

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Citing Article(s) :

1. Progress of Theoretical Physics Vol. 45 No. 1 (1971) pp. 324-326 :

   On Superconductivity of Lanthanum and Uranium

   Takashi Kusakabe

2. Progress of Theoretical Physics Vol. 45 No. 1 (1971) pp. 329-330 :

   On Effect of Non-Magnetic Impurities on Superconductivity of a Two-Band Model

   Takashi Kusakabe

3. Progress of Theoretical Physics Vol. 45 No. 5 (1971) pp. 1376-1381 :

   Non-Magnetic Resonance Scattering in Two-Band Superconductors

   Takashi Kusakabe

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