Two-gap superconductivity in Ba1-xKxFe2As2: A complementary study of the magnetic penetration depth by μSR and ARPES
Abstract
We investigate the magnetic penetration depth λ in superconducting Ba1-xKxFe2As2 (Tc32K) with muon-spin rotation (μSR) and angle-resolved photoemission (ARPES). Using μSR, we find the penetration-depth anisotropy γλ=λc/λab and the second-critical-field anisotropy γHc2 to show an opposite T-evolution below Tc. This dichotomy resembles the situation in the two-gap superconductor MgB2. A two-gap scenario is also suggested by an inflection point in the in-plane penetration depth λab around 7K. The complementarity of μSR and ARPES allows us to pinpoint the values of the two gaps and to arrive to a remarkable agreement between the two techniques concerning the full T-evolution of λab. This provides further support for the described scenario and establishes ARPES as a tool to assess macroscopic properties of the superconducting condensate.