Disorder effects in multiorbital $s_{\pm }$-wave superconductors: Implications for Zn-doped BaFe${}_2$As${}_2$ compounds

Abstract

Recent experiments on Zn-doped 122-type iron pnictides, Ba(Fe${}_{1-x-y}$Co${}_y$Zn${}_x$)${}_2$As${}_2$, are challenging our understanding of electron doping the 122s and the interplay between doping and impurity scattering. To resolve this enigma, we investigate the disorder effects of nonmagnetic Zn impurities in the strong (unitary) scattering limit on various properties of the system in the $s_{\pm }$-wave superconducting pairing state. The lattice Bogoliubov-de Gennes equation (BdG) is solved self-consistently based on a minimal two-orbital model with an extended range of impurity concentrations. We find that Zn impurity is best modeled as a defect, where charge is mainly localized, but scattering is extended over a few lattice sites. With increasing Zn concentration the density of states shows a gradual filling of the gap, revealing the impurity-induced pair breaking effect. Moreover, both the disorder configuration-averaged superconducting order parameter and the superfluid density are dramatically suppressed towards the dirty limit, indicating the violation of the Anderson theorem for conventional s-wave superconductors and the breakdown of the Abrikosov-Gorkov theory for impurity-averaged Green's functions. Furthermore, we find that the superconducting phase is fully suppressed close to the critical impurity concentration of roughly $n_{\text{imp}}\approx 10$, in agreement with recent experiments.

12 pages, 7 figures, v2 with figure revised

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Cited by in corpus (14)

• Impurities in multiband superconductors
• Unexpected impact of magnetic disorder on multiband superconductivity
• Progress in nonmagnetic impurity doping studies on Fe-based superconductors
• Robustness of quantum critical pairing against disorder
• Temperature-dependent $s_{\pm }\leftrightarrow s_{++}$ transitions in the multiband model for Fe-based superconductors with impurities
• Details of the disorder-induced transition between $s_{\pm }$ and $s_{++}$ states in two-band model for Fe-based superconductors
• Edge states and local electronic structure around an adsorbed impurity in a topological superconductor
• Evolution of quasiparticle states with and without a Zn-impurity in doped 122 iron pnictides
• Uniform impurity scattering in two-band $s_{\pm }$ and $s_{++}$ superconductors
• Modulation of pairing symmetry with bond disorder in unconventional superconductors
• Decisive proofs of the $s_{\pm }\to s_{++}$ transition in the temperature dependence of the magnetic penetration depth
• Effects of single- and multi-substituted Zn ions in doped-122 type iron-based superconductors
• Emergent topological mirror insulator in t2g-orbital systems
• Phase diagram of the isovalent phosphorous-substituted 122-type iron pnictides