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 (FSs) 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 (∼65K) than what has been observed. © 2013 American Physical Society.