Determination of the Electron–Phonon Coupling Constants from the Experimental Temperature Dependences of Superconducting Gaps in MgB2статья

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Дата последнего поиска статьи во внешних источниках: 7 декабря 2016 г.

Работа с статьей

[1] Kuzmichev S. A., Kuzmicheva T. E., Tchesnokov S. N. Determination of the electron–phonon coupling constants from the experimental temperature dependences of superconducting gaps in mgb2 // JETP Letters. — 2014. — Vol. 99, no. 5. — P. 295–302. Experimental temperature dependences Δ_{σ,π}(T) of the energy of superconducting gaps for MgB2 samples with the critical temperatures 22 K < Tc < 41 K have been fitted by selecting the renormalized electron–phonon coupling constants λ_ij with the use of the Moskalenko–Shul system of equations, the expression for the frequency of collective plasma oscillations obtained by Leggett for two-gap superconductors, and two fitting parameters. We previously obtained the dependences Δ_{σ,π}(T) by the multiple Andreev reflection spectroscopy of superconductor–constriction–superconductor junctions based on MgB2 with various degree of disorder of the crystal structure. It has been shown that the intraband pairing constants are decisive for the superconductivity mechanism in MgB2; in this case, (V_σσ * V_ππ)^0.5 / V_σπ = 8-–22 and the ratio of the interband constants can range from 3 to 11. The set of the Eliashberg coupling constants λ_{ij}^0 has been qualitatively determined for relatively pure MgB2 with maximum values Tc ≈ 40 K. The leading constant is 0.7 < λ_{σσ}^0 ≈ λ_{eff}^0 < 0.9 and depends on the choice of the upper integration limit in the Bardeen–Cooper–Schrieffer (BCS) model and the effective Coulomb repulsion μ_{eff}^*. The characteristic ratio for the gap in the σ band is 2Δ_σ/kBTc = 5.0–-6.5. [ DOI ]

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