Superconductivity and its Enhancement under High Pressure in "F-free" Single Crystals of CeOBiS$_2$

Masashi Tanaka; Masanori Nagao; Ryo Matsumoto; Noriyuki Kataoka; Ikuo Ueta; Hiromi Tanaka; Satoshi Watauchi; Isao Tanaka; Yoshihiko Takano

doi:10.1016/j.jallcom.2017.06.125

arXiv · 1706.03590

Superconductivity and its Enhancement under High Pressure in "F-free" Single Crystals of CeOBiS$_2$

Masashi Tanaka·Masanori Nagao·Ryo Matsumoto·Noriyuki Kataoka·Ikuo Ueta·Hiromi Tanaka·Satoshi Watauchi·Isao Tanaka·Yoshihiko Takano

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Abstract

"F-free" CeOBiS$_2$ single crystals have successfully grown, thoroughly eliminating a concern about F-contamination by using a high-purity CsCl flux. The obtained crystals have a plate-like shape with a size of 1.0-3.0 mm in the well-developed plane. Single crystal X-ray structural analysis clearly revealed that the CeOBiS$_2$ crystallizes with a space group $P4/nmm$ (with lattice parameters of $a$ = 4.0189(6) {\AA}, $c$ = 13.573(2) {\AA}). The bond valence sum estimation and X-ray photoelectron spectroscopy analysis showed that the chemical state of Ce was in the mixed valence of Ce$^{3+}$ and Ce$^{4+}$. The single crystals show superconductivity with zero resistivity at $\sim$1.3 K. This is the first conclusive evidence of superconductivity driven by Ce valence fluctuation in surely non-doped CeOBiS$_2$. The superconducting transition temperature was enhanced up to $\sim$3.8 K by applying hydrostatic pressure.

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Masashi Tanaka, Masanori Nagao, Ryo Matsumoto, Noriyuki Kataoka, Ikuo Ueta, Hiromi Tanaka, Satoshi Watauchi, Isao Tanaka, Yoshihiko Takano. 2017-06-12. Superconductivity and its Enhancement under High Pressure in "F-free" Single Crystals of CeOBiS$_2$. https://doi.org/10.1016/j.jallcom.2017.06.125

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