Multigap Superconductivity in RbCa2Fe4As4F2 Investigated Using μSR Measurements

The superconducting properties of the recently discovered high-T, superconductor RbCa2Fe4As4F2 with double Fe2As2 layers and T-c approximate to 30 K have been investigated using magnetization, heat capacity, transverse-field (TF) and zero-field (ZF) muon-spin rotation/relaxation (mu SR) measurements. Low field magnetization and heat capacity (C-p) measurements reveal an onset of bulk superconductivity with T-c similar to 30.0(4) K, where there is a jump at T-c of Delta C-p/T-c = 94.6 (mJ/mole-K-2). The temperature dependence of the magnetic penetration depth obtained from transverse-field (TF) mu SR is better described by the two-gap s + s and s + d models than the single gap s- or d-wave scenarios. The presence of two superconducting gaps in RbCa2Fe4As4F2 is consistent with the multigap superconductivity observed in other Fe-based superconductors, including ACa(2)Fe(4)As(4)F(2) (A = K and Cs). From the TF-mu SR study, an in-plane magnetic penetration depth of lambda(ab)(0) = 231.5(3) nm, a superconducting carrier density n(s) = 1.29(1) x 10(27) m(-3), and an effective mass of the carriers of m* = 2.45(1)m(e) are estimated. Zero-field mu SR measurements do not reveal clear signs of time reversal symmetry breaking below T-c, but the temperature dependence of the relaxation of the asymmetry between 150 and 1.2 K may indicate the presence of spin-fluctuations.