Anisotropy effects on the critical magnetic field in CaC${}_6$ superconductor

Abstract

The calcium intercalated graphite (CaC${}_6$) is considered to be a representative material of the graphite intercalated superconductors, which exhibits sizable anisotropy of the Fermi surface (FS). Herein, the influence of the FS anisotropy on the critical magnetic field ($H_C$) in CaC${}_6$ superconductor is comprehensively analyzed within the Migdal-Eliashberg (M-E) formalism. To precisely account for the mentioned anisotropy effects, the analysis is conducted in the framework of the six-band approximation, hitherto not employed for calculations of the $H_C$ function in CaC${}_6$ material. For convenience, the obtained results are compared with the available one- and three-band estimates reported by using the M-E theory. A notable signatures of the increased number of bands are observed for the temperature dependent $H_C$ functions. In particular, the $H_C$ function decreases at T=0 K as the number of the considered bands is higher. Moreover, it is argued that the six-band formalism yields the most physically relevant shape of the $H_C$ function among all considered approximations. Therefore, the six-band model introduces not only quantitative but also qualitative changes to the results, in comparison to the other discussed FS approximations. This observation supports postulate that the six-band model constitutes minimal structure for FS of CaC${}_6$, but also magnify importance of anisotropy effects for the critical magnetic field calculations.

References in corpus (11)

• The PseudoDojo: Training and grading a 85 element optimized norm-conserving pseudopotential table
• Optimization Algorithm for the Generation of ONCV Pseudopotentials
• Superconductivity in the Intercalated Graphite Compounds C6Yb and C6Ca
• Superconductivity of bulk CaC6
• Evidence for superconductivity in Li-decorated monolayer graphene
• First-principles Green's-function method for surface calculations: a pseudopotential localized basis set approach
• Superconductivity in Heavy Alkaline-Earths Intercalated Graphites
• First-principles calculations of the superconducting properties in Li-decorated monolayer graphene within the anisotropic Migdal-Eliashberg formalism
• Role of Coulomb interaction in the superconducting properties of CaC6 and H under pressure
• Superconducting properties of lithium-decorated bilayer graphene
• Superconducting properties of under- and over-doped Ba${}_x$K${}_{1-x}$BiO${}_3$ perovskite oxide