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arXiv · 1301.2668

Influence of microstructure on superconductivity in K$_x$Fe$_{2-y}$Se$_2$ and evidence for a new parent phase K$_2$Fe$_7$Se$_8$

Xiaxin Ding·Delong Fang·Zhenyu Wang·Huan Yang·Jianzhong Liu·Qiang Deng·Guobin Ma·Chong Meng·Yuhui Hu·Hai-Hu Wen
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Abstract

The search for new superconducting materials has been spurred on by the discovery of iron-based superconductors whose structure and composition is qualitatively different from the cuprates. The study of one such material, K$_x$Fe$_{2-y}$Se$_2$ with a critical temperature of 32 K, is made more difficult by the fact that it separates into two phases: a dominant antiferromagnetic insulating phase with a K$_2$Fe$_4$Se$_5$ structure, and a minority superconducting phase whose precise structure is as yet unclear. Here we perform electrical and magnetization measurements, scanning electron microscopy and microanalysis, X-ray diffraction, and scanning tunnelling microscopy on K$_x$Fe$_{2-y}$Se$_2$ crystals prepared under different quenching processes to better understand the relationship between its microstructure and its superconducting phase. We identify a 3D network of superconducting filaments within this material and present evidence to suggest that the superconducting phase consists of a single Fe vacancy for every eight Fe-sites arranged in a $\sqrt{10}\times\sqrt{8}$ parallelogram structure.

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Xiaxin Ding, Delong Fang, Zhenyu Wang, Huan Yang, Jianzhong Liu, Qiang Deng, Guobin Ma, Chong Meng, Yuhui Hu, Hai-Hu Wen. 2013-01-12. Influence of microstructure on superconductivity in K$_x$Fe$_{2-y}$Se$_2$ and evidence for a new parent phase K$_2$Fe$_7$Se$_8$. https://doi.org/10.1038/ncomms2913 10.1038/s41467-020-14681-7

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