Dislocation Arrays Hosting Topological Bound States in Epitaxial Tetragonal FeSe Films

Abstract

Topological defects in real space can host robust, localized quantum states for quantum information processing and sensing, yet deterministic control over their formation in crystalline materials remains challenging. Here, we show that symmetry-mismatched epitaxy of tetragonal FeSe films on SrTiO3(111) naturally generates networks of screw dislocations and tilt grain boundaries composed of periodic arrays of edge dislocations. Low-temperature scanning tunneling microscopy/spectroscopy measurements reveal localized electronic states pinned to these dislocation cores. Combined with first-principles calculations, we identify these states as topological bound states arising from the interplay between the real-space topological invariant of the defect, the Burgers vector, and the nontrivial electronic topology of FeSe. Our work demonstrates symmetry mismatch epitaxy as a scalable route toward template topological defect networks and their associated quantum states in solid-state materials.