Intrinsic high-temperature superconductivity in ternary iron selenides

Abstract

We examine superconductivity in the mesoscopically mixed antiferromagnetic(AF) and superconducting (SC) phases of ternary iron selenides K${}_y$Fe${}_{2-x}$Se${}_2$. It is shown that the interlayer hopping and AF order are key factors to determine $T_c$ of the SC phase. In general, the hopping will produce deformed Fermi surfaces (FS's) that tend to suppress superconductivity. However, contrary to the common expectation, we find that larger AF order actually results in larger SC order, which explains the observed relatively high $T_c$ in these phases. Furthermore our results indicate that by reducing the interlayer hopping appropriately, phase-separated K${}_y$Fe${}_{2-x}$Se${}_2$ may exhibit its intrinsic SC phase in the two dimensional limit with a much higher $T_c$ ($\sim 65K$) than what has been observed.

7 pages, 7 figures. Accepted for publication as a Regular Article in Physical Review B

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• Optical conductivity of iron-based superconductors
• High resolution characterisation of microstructural evolution in Rb${}_x$Fe${}_{2-y}$Se${}_2$ crystals on annealing
• Tuning orbital-selective correlation effects in superconducting Rb${}_{0.75}$Fe${}_{1.6}$Se${}_{2-z}$S${}_z$
• Raman spectroscopy of K_xCo_{2-y}Se_2 single crystals near the ferromagnet-paramagnet transition
• Multiband behavior and non-metallic low-temperature state of K${}_{0.50}$Na${}_{0.24}$Fe${}_{1.52}$Se${}_2$