In-Plane Differentiation and Out-of-Plane Coherence in Superconducting K 2-x Fe 4+y Se 5
The origin of high-Tc superconductivity in K2-xFe4+ySe5 is resolved by identifying a novel 'stripe-type orthorhombic phase' as the true parent phase. This parent phase requires a subsequent structural distortion to become superconducting. Superconductivity arises from this two-step transition, where the metallic phase locks into the magnetic scaffold created by the stripe structure, explaining high-Tc amplification through controlled nanoscale heterogeneity.