Superfluid density and superconducting gaps of RbFe2As2 as a function of hydrostatic pressure

Abstract

The superfluid density and superconducting gaps of superconducting RbFe2As2 have been determined as a function of temperature, magnetic field, and hydrostatic pressure by susceptibility and muon-spin spectroscopy measurements. From the data, fundamental microscopic parameters of the superconducting state like the London penetration depth λ, the gap values Δ, the upper critical field Bc2, and the Ginzburg-Landau parameter κ have been obtained. In accordance with earlier measurements the ratio of the superfluid density ns λ-2 to the superconducting transition temperature T c=2.52(2) K at ambient pressure is found to be much higher in the strongly hole-overdoped RbFe2As2 than in high-T c Fe-based and other unconventional superconductors. As a function of pressure, Tc strongly decreases, at the rate of T c/dp=-1.32 K GPa-1, i.e., it is reduced by 52% at p=1 GPa. The temperature dependence of ns is best described by a two-gap s-wave model, with both superconducting gaps being decreased by hydrostatic pressure until the smaller gap completely disappears at p=1 GPa.