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首页> 外文期刊>JETP Letters >Determination of the Electron-Phonon Coupling Constants from the Experimental Temperature Dependences of Superconducting Gaps in MgB_2
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Determination of the Electron-Phonon Coupling Constants from the Experimental Temperature Dependences of Superconducting Gaps in MgB_2

机译：从MgB_2中超导缝隙的实验温度依赖性确定电子-声子耦合常数

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摘要

Experimental temperature dependences Δ_(σ, π)(T) of the energy of superconducting gaps for MgB_2 samples with the critical temperatures 22 K < T_c < 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 MgB_2 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 MgB_2; in this case, √V_(σσ)V_(σπ)/V_(σπ) = 8-22 and the ratio of the interband constants α can range from 3 to 11. The set of the Eliashberg coupling constants λ_(ij) has been qualitatively determined for relatively pure MgB_2 with maximum values T_c ≈ 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 is2Δ_σ/k_BT_c = 5.0-6.5.
机译：临界温度为22 K

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