Boundary Current Response in Ba K FeAs Single Crystal Probed by Non-resonant Microwave Absorption.

Non-resonant microwave absorption (NRMA) in superconducting materials has become a new experimental technique to probe and understand superconducting materials. For example, cuprate superconductors are well studied with this technique. At the same time, the technique is also evolving. This NRMA technique has been used to study magnetic shielding effects/boundary current in Ba. K .FeAs (BaK122) single crystals of iron pnictide superconducting sample measured at 9.4 GHz below T (4.2-32 K). It has been observed that a small modulation field used in NRMA experiment yields the boundary current response. We have established that the boundary current response depends on both the modulation amplitude and the temperature. At high modulation field amplitudes and temperatures close to T , the boundary current response gets suppressed and the flux-modulated response dominates. At low temperatures far away from T , only the boundary current response dominates. [ABSTRACT FROM AUTHOR]