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arXiv · 1012.5552

Superconductivity and Magnetic Properties of high-quality single crystals of $A_{x}$Fe$_2$Se$_2$ ($A$ = K and Cs)

J. J. Ying·X. F. Wang·X. G. Luo·A. F. Wang·M. Zhang·Y. J. Yan·Z. J. Xiang·R. H. Liu·P. Cheng·G. J. Ye·X. H. Chen
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Abstract

We successfully grew the high-quality single crystals of $A_{x}$Fe$_2$Se$_2$ ($A$ = K and Cs) by self-flux method. Sharp superconducting transition was observed for both types of crystals. The crystals show the onset superconducting transition temperatures ($T_{\rm c}$) of 31 K and 30 K for K- and Cs-compounds, respectively, with nearly 100% shielding fraction. The crystals show quite high resistivity in the normal state of more than 160 m$Ω$ cm and 1300 m$Ω$ cm maximum resistivity for $K_{0.86}Fe_2Se_{1.82}$ and $Cs_{0.86}Fe_{1.66}Se_{2}$ single crystals, respectively. Much larger upper critical field $H_{\rm c2}$ is inferred from low-temperature iso-magnetic-field magnetoresistance in these crystals than in FeSe. The anisotropy $H^{ab}_{\rm c2}$(0)/$H^{c}_{\rm c2}$(0) is around 3 for both of the two materials. Anisotropic peculiar magnetic behavior in normal state has been found for $Cs_{0.86}Fe_{1.66}Se_{2}$

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J. J. Ying, X. F. Wang, X. G. Luo, A. F. Wang, M. Zhang, Y. J. Yan, Z. J. Xiang, R. H. Liu, P. Cheng, G. J. Ye, X. H. Chen. 2010-12-27. Superconductivity and Magnetic Properties of high-quality single crystals of $A_{x}$Fe$_2$Se$_2$ ($A$ = K and Cs). https://doi.org/10.1103/physrevb.83.212502

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