Superconducting properties of hole doped Ba0.6Li0.4Fe2As2 single crystal.

Journal of physics. Condensed matter : an Institute of Physics journal

PubMedID: 24721709

Ahmad D, Min BH, Ko MJ, Seo YL, Choi WJ, Lee JH, Kim GC, Kim YC, Kwon YS. Superconducting properties of hole doped Ba0.6Li0.4Fe2As2 single crystal. J Phys Condens Matter. 2014;26(17):175701.
We report the emergence of superconductivity in Li doped Ba-122 single crystals grown by the Bridgman method. The superconducting transition temperature Tc,onset is around 19?K. The specific heat capacity C/T shows a weak anomaly near Tc. The value of ?C/?nTc is smaller than the value predicted in BCS theory indicating a multigap nature of the sample. The magnetic measurements show that the lower critical field Hc1(T) exhibits a linear temperature dependence, with a pronounced change of the Hc1(T) curvature around 0.4Tc and Hc1(0) ˜ 430?Oe in the Ba0.6Li0.4Fe2As2 single crystal. Furthermore, temperature dependence of the penetration depth ?(T) follows a power law (~T(n)) below 0.4Tc which predicts possible S±-wave pairing in a Ba0.6Li0.4Fe2As2 superconductor. Over a wide range of temperatures, the Jc(H) exhibits a relation [Formula: see text] with a = 0.5 ~ 0.6 for H || c and H || ab which indicates random defects in the sample. We found that the temperature dependence of the critical current density Jc(T) can be fitted well with the [Formula: see text]-type pinning model, whose origin is attributed to spatial variations of charge carrier mean free path [Formula: see text]. We suggest that the large mismatch in the ionic radius of Ba and Li can affect the irreversible magnetic properties of the Ba0.6Li0.4Fe2As2 single crystal without any structural transition.