Zero-Field muSR Search for a Time-Reversal-Symmetry-Breaking Mixed Pairing State in Superconducting Ba1-xKxFe2As2

Abstract

We report the results of a zero-field muon spin relaxation (ZF-µSR) study of superconducting Ba1−xKxFe2As2 (0.5 ≤ x ≤ 0.9) in search of weak spontaneous internal magnetic fields associated with proposed time-reversal-symmetry breaking mixed pairing states. The measurements were performed on polycrystalline samples, which do not exhibit the mesoscopic phase separation previously observed in single crystals of Ba1−xKxFe2As2. No evidence of spontaneous internal magnetic fields is found in any of the samples at temperatures down to T ∼ 0.02 K.