Evolution of superconductivity in isovalent Te-substituted K x Fe 2−y Se 2 crystals

Author： Ozaki Toshinori   Takeya Hiroyuki   Deguchi Keita   Demura Satoshi   Hara Hiroshi   Watanabe Tohru   Saleem James Denholme   Okazaki Hiroyuki   Fujioka Masaya   Yokota Yoshiko   Yamaguchi Takahide   Takano Yoshihiko  

Publisher： IOP Publishing

ISSN： 0953-2048

Source： Superconductor Science and Technology, Vol.26, Iss.5, 2013-05, pp. : 55002-55006

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Abstract

We report the evolution of superconductivity and the phase diagram of the KxFe2−ySe2−zTez (z = 0-0.6) crystals grown by a one-step synthesis. The one-step synthesis is much simpler than a conventional process to grow the KxFe2−ySe2 system. No structural transition is observed in any crystals, while lattice parameters exhibit a systematic expansion with increasing Te content. The Tc exhibits a gradual decrease with increasing Te content from &${T}_{mathrm{c}}^{mathrm{onset}}=3 2.9$; K at z = 0 to &${T}_{mathrm{c}}^{mathrm{zero}}=2 7.9$; K at z = 0.5, followed by a sudden suppression of superconductivity at z = 0.6. Upon approaching a Te concentration of 0.6, the shielding volume fraction decreases and eventually drops to zero. Simultaneously, hump positions in the ρ-T curve shift to lower temperatures. These results suggest that isovalent substitution of Te for Se in KxFe2−ySe2 crystals suppresses the superconductivity in this system.

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