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Chemical potential influence on the condensation energy from a Boson-Fermion model of superconductivity
Physica C: Superconductivity and its Applications ( IF 1.7 ) Pub Date : 2022-06-07 , DOI: 10.1016/j.physc.2022.1354090
I. Chávez, P. Salas, O.A. Rodríguez, M.A. Solís, M. de Llano

Influence of the temperature dependent chemical potential on the condensation energy from a ternary Boson-Fermion model of superconductivity is reported, it consist of unbound electrons/holes which are fermions plus two-electron and two-hole Cooper pairs which are bosons. When solving simultaneously the set of equations of the mixture (two gap-like equations, one for electron pairs and another one for hole pairs, plus the particle number conservation equation) within the weak-coupling (BCS regime), the resulting superconducting chemical potential shows a shift from its normal state counterpart, which is related to both the magnitude of the temperature-dependent superconducting gap and to the Fermi energy of the superconductor. As predicted by van der Marel in the early 1990s we also find that the superconducting chemical potential has a prominent kink at critical temperature Tc, which in turn coincides with the normal state chemical potential. Also there is a discontinuity in its first derivative which directly affects the magnitude in the specific heat jump. We show that the difference between the superconducting and normal state chemical potentials is of the same order of magnitude as the corresponding difference between the thermodynamic potentials for the mixture, and must therefore be accounted for in the condensation energy calculations instead of ignoring it as is done often. The condensation energy obtained here shows very good agreement with experimental data for elemental superconductors.



中文翻译:

超导玻色子-费米子模型中化学势对凝聚能的影响

报告了温度依赖性化学势对超导三元玻色子-费米子模型的凝聚能的影响,它由费米子的未束缚电子/空穴加上玻色子的二电子和二空穴库珀对组成。当同时求解弱耦合(BCS 方案)内的混合物方程组(两个类间隙方程,一个用于电子对,另一个用于空穴对,加上粒子数守恒方程)时,得到的超导化学势显示了与其正常状态对应物的转变,这与温度相关的超导间隙的大小和超导体的费米能量有关。C,这又与正常状态的化学势一致。其一阶导数也存在不连续性,直接影响比热跃变的大小。我们表明,超导和正常状态化学势之间的差异与混合物的热力学势之间的相应差异具有相同的数量级,因此必须在冷凝能计算中加以考虑,而不是像所做的那样忽略它经常。这里获得的凝聚能与元素超导体的实验数据非常吻合。

更新日期:2022-06-08
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