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首页> 外文期刊>Physica, C. Superconductivity and its applications >Two-band superconductivity in (AlMg)B-2: Critical temperature and isotope exponent as a function of carrier density
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Two-band superconductivity in (AlMg)B-2: Critical temperature and isotope exponent as a function of carrier density

机译：（AlMg）B-2中的两波段超导性：临界温度和同位素指数与载流子密度的关系

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摘要

We consider as a minimal model for superconductivity in (AlMg)B-2 a two-band superconductor, having an anisotropic electronic structure described by two tight binding bands, considering a pairing scenario driven by an attractive interaction in which the interband pairing terms assume an important role. We solve the two-gap equations at the critical temperature T = T-c and calculate T-c and the chemical potential mu as a function of the number of carriers n for various values of pairing interaction, V, and cut-off energy, omega(c). Using a self-consistent approach developed in a previous paper by two of the present authors, we calculate the isotope exponent alpha as a function of mu. We find that the isotope exponent shows a minimum in the energy range around a dimensional electronic topological transition (ETT) where the Fermi surface of one of the bands changes from 2D to 3D dimensionality. We have been able to fix the parameters of the theory, namely, the attractive interaction, V, and the cut-off frequency, omega(c), by imposing experimental constraints on alpha, T-c and mu for undoped MgB2, specifically, 0.3, 40 K and 1.8 eV, respectively. (C) 2008 Elsevier B.V. All rights reserved.
机译：考虑到由有吸引力的相互作用驱动的配对情况，其中带间配对项假定为一个，因此，我们将具有两个紧密结合带描述的各向异性电子结构的两频带超导体视为（AlMg）B-2中超导的最小模型。重要角色。我们在临界温度T = Tc时求解两个间隙方程，并针对各种互配作用V和截止能量omega（c），计算Tc和化学势mu作为载流子数n的函数。使用两位作者在前一篇论文中开发的自洽方法，我们计算了同位素指数α作为mu的函数。我们发现，同位素指数在一个维电子拓扑跃迁（ETT）周围的能量范围内显示最小值，其中一个能带的费米表面从2D变为3D维。通过对无掺杂的MgB2的alpha，Tc和mu施加实验约束，我们已经能够确定该理论的参数，即有吸引力的相互作用V和截止频率omega（c），分别为40 K和1.8 eV。 （C）2008 Elsevier B.V.保留所有权利。

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