Evolution of superconductivity in isovalent Te-substituted K sub(x)Fe sub(2-y)Se sub(2) crystals

• Published in: Superconductor science & technology Vol. 26; no. 5; pp. 1 - 5
• Main Authors: Ozaki, Toshinori, Takeya, Hiroyuki, Deguchi, Keita, Demura, Satoshi, Hara, Hiroshi, Watanabe, Tohru, Denholme, Saleem James, Okazaki, Hiroyuki, Fujioka, Masaya, Yokota, Yoshiko, Yamaguchi, Takahide, Takano, Yoshihiko
• Format: Journal Article
• Language: English
• Published: 01.01.2013
• Subjects: Crystal structure; Crystals; Evolution; Lattice parameters; Phase diagrams; Superconductivity; Superconductors; Synthesis
• ISSN: 0953-2048; 1361-6668
• DOI: 10.1088/0953-2048/26/5/055002

We report the evolution of superconductivity and the phase diagram of the K sub(x)Fe sub(2-y)Se sub(2-z)Te sub(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 K sub(x)Fe sub(2-y)Se sub(2) system. No structural transition is observed in any crystals, while lattice parameters exhibit a systematic expansion with increasing Te content. The T sub(c) exhibits a gradual decrease with increasing Te content from T super(onset) sub(c) = 32.9 K at z = 0 to T super(zero) sub(c) = 27.9 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 [rho]-T curve shift to lower temperatures. These results suggest that isovalent substitution of Te for Se in K sub(x)Fe sub(2-y)Se sub(2) crystals suppresses the superconductivity in this system.