Intrinsic Percolative Superconductivity in KxFe2-ySe2 Single Crystals

TL;DR

This study investigates the magnetic properties of KxFe2-ySe2 single crystals, revealing intrinsic percolative superconductivity characterized by unusual magnetic penetration and hysteresis behaviors.

Contribution

It provides evidence for intrinsic percolative superconductivity in KxFe2-ySe2, highlighting weakly coupled superconducting islands as the underlying mechanism.

Findings

Small full-magnetic-penetration field of 300 Oe at 2 K

Vanishing central peak in magnetization hysteresis loops below 13 K

Smaller MHL width compared to related compounds

Abstract

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 (Hp1= 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 the relatives Ba0.6K0.4Fe2As2 and Ba(Fe0.92Co0.08)2As2, and the MHLs in the latter two samples show the normal central peak near zero field. All these anomalies found in KxFe2-ySe2 can be understood in the picture that the sample is percolative with weakly coupled superconducting islands.