Nodal multigap superconductivity in the anisotropic iron-based compound RbCa2Fe4As4F2

Abstract The 12442 compounds are a recently discovered family of iron-based superconductors, that share several features with the cuprates due to their strongly anisotropic structure, but so far poorly understood. Here, we report on gap structure and anisotropy RbCa 2 (Fe 1− x Ni ) 4 As F single crystals, investigated by combination directional point-contact Andreev-reflection spectroscopy coplanar waveguide resonator measurements. Two gaps were identified, clear signatures d -wave-like nodal structures which persist upon doping, well described two-band − state symmetry-imposed nodes. A large London penetration depth was revealed, weakly dependent temperature fully compatible model.