Anisotropic two-band α-model and its application to layered chalcogenide superconductor NbSe₂

The generalized α-model for anisotropic two-band superconductivity is consistently constructed with the consideration of weak interband electron–electron interaction. Tailored from the two-band BCS theory, the developed framework can be applied to investigate thermodynamic properties of intraband strong-coupling superconductors. Accordingly, we perform a calculation on the temperature dependence of specific heat and obtain an analytic expression for specific heat jump at the superconducting critical temperature. Meanwhile, we also compute the superfluid density and the spin susceptibility with this formalism. Given the low-temperature superconducting gaps from experimental measurement, all of our theoretical results can fit the experimental data of the layered two-band superconductor NbSe₂ well.