Controlling superconductivity via electron doping in YFe₂Ge₂

Iron-based superconductors are a valuable platform to study the interplay of magnetism and unconventional superconductivity. YFe₂Ge₂ stands out because it does not contain pnictogen or chalcogen elements and its Fermi surface is more three-dimensional [1]. Bulk superconductivity in YFe₂Ge₂ was discovered with a transition temperature of about 1.8 K in single crystals [2], yet heat capacity measurements indicate that the superconducting gap has a sign-changing nature [3], and the exact symmetry remains an open question. The compound can be represented as Y³⁺(Fe^2.5+)₂(Ge^4-)₂ , showing that the Fe atoms are hole doped relative to the typical Fe²⁺ configuration. We use density functional theory calculations and the random phase approximation to calculate the pairing potential. The gap symmetry and pairing strength are studied as a function of electron doping.

[1] Y. Zou et al., Phys. Status Solidi RRL 8, 11, 928–930 (2014).

[2] D. J. Singh, Phys. Rev. B 89, 024505 (2014).

[3] J. Chen et al., Phys. Rev. Lett. 125, 237002 (2020).