Intrinsic percolative superconductivity in KxFe2−ySe2 single crystals
Institute of Physics and Beijing National Laboratory for Condensed Matter Physics, Chinese Academy of Sciences - P.O. Box 603, Beijing 100190, China
2 Department of Physics, Renmin University of China - Beijing 100872, China
3 National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University Nanjing 210093, China
Accepted: 14 September 2011
Magnetic field penetration and magnetization hysteresis loops (MHLs) have been measured in KxFe2−ySe2 single crystals. The magnetic field penetration shows a two-step feature with a very small full-magnetic-penetration field (≈300 Oe at 2 K), and accordingly the MHL exhibits an abnormal vanishing of the central peak near zero field below 13 K. The width of the MHL in KxFe2−ySe2 at the same temperature is in general much smaller than that measured in Ba0.6K0.4Fe2As2 and Ba(Fe0.92Co0.08)2As2, and the MHLs in the latter two samples show a normal central peak near zero field. All these anomalies found in KxFe2−ySe2 can be understood in the sense that the sample is percolative with weakly coupled superconducting islands.
PACS: 74.20.Rp – Pairing symmetries (other than s-wave) / 74.70.Dd – Ternary, quaternary, and multinary compounds (including Chevrel phases, borocarbides, etc.) / 74.25.Ha – Magnetic properties including vortex structures and related phenomena
© EPLA, 2011