Muon-spin rotation measurements of the magnetic penetration depth in the iron-based superconductor Ba1-xRbxFe2As2

Measurements of the magnetic penetration depth. in the Fe-based superconductor Ba1-xRbxFe2As2 (x = 0.3, 0.35, 0.4) were carried out using the muon-spin rotation (mu SR) technique. The temperature dependence of. is well described by a two-gap s + s-wave scenario with a small gap Delta(1) approximate to 1-3 meV and a large gap Delta(2) approximate to 7-9 meV. By combining the present data with those previously obtained for RbFe2As2 a decrease of the BCS ratio 2 Delta(2)/k(B)T(c) with increasing Rb content x is observed. On the other hand, the BCS ratio 2 Delta(1)/k(B)T(c) is almost independent of x. In addition, the contribution of Delta(1) to the superfluid density is found to increase with x. These results are discussed in light of the suppression of interband processes upon hole doping.