Intrinsic high-temperature superconductivity in ternary iron selenides

TL;DR

This paper investigates the factors influencing high-temperature superconductivity in ternary iron selenides, revealing that antiferromagnetic order enhances superconductivity and suggesting ways to achieve higher $T_c$ through structural modifications.

Contribution

It demonstrates that larger AF order can increase $T_c$ and proposes that reducing interlayer hopping can realize an intrinsic 2D superconducting phase with higher $T_c$.

Findings

Larger AF order correlates with higher $T_c$.

Interlayer hopping suppresses superconductivity.

Reducing interlayer hopping could lead to $T_c$ around 65K.

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.