## Phase Diagram of ${\mathrm{K}}_{x}{\mathrm{Fe}}_{2-y}{\mathrm{Se}}_{2-\mathit{z}}{\mathbf{S}}_{\mathit{z}}$ and the Suppression of its Superconducting State by an $\mathrm{Fe}2\text{-}\mathrm{Se}/\mathbf{S}$ Tetrahedron Distortion

We report structurally tuned superconductivity in a K x Fe 2 - y Se 2 - z S z ( 0 ≤ z ≤ 2 ) phase diagram. Superconducting T c is suppressed as S is incorporated into the lattice, eventually vanishing at 80% of S. The magnetic and conductivity properties can be related to stoichiometry on a poorly occupied Fe1 site and the local environment of a nearly fully occupied Fe2 site. The decreasing T c coincides with the increasing Fe1 occupancy and the overall increase in Fe stoichiometry from z = 0 to z = 2 . Ourmore »