A study of the temperature and field dependence of the penetration depth λ of the superconductor RbFe2As2(Tc=2.52 K) was carried out by means of muon-spin rotation measurements. In addition to the zero-temperature value of the penetration depth λ(0)=267(5) nm, a determination of the upper critical field Bc2(0)=2.6(2) T was obtained. The temperature dependence of the superconducting carrier concentration is discussed within the framework of a multigap scenario. Compared to the other “122” systems which exhibit much higher Fermi level, a strong reduction in the large gap BCS ratio 2Δ/kBTc is observed. This is interpreted as a consequence of the absence of interband processes. Indications of possible pair-breaking effect are also discussed.
© 2010 The American Physical Society