Moiré reconstruction at a twisted SrTiO3 interface

Abstract

Twisted oxide double layers have emerged as a promising platform for exploring moiré physics, including polar topologies and emergent electronic phases. However, the intrinsic complexity of oxide surfaces, such as contamination, roughness, and the presence of two distinct terminations (AO and BO2), can complicate the identification of buried interfacial structures. Here, using atomically flat SrTiO3 membranes with a predominantly SrO-TiO2 interfacial configuration, we directly visualize a moiré-periodic structural reconstruction at the buried interface that is distinct from the geometric moiré of rigid stacking. The reconstructed interface hosts head-to-head-like polar distortions, moiré-modulated Ti electronic structure, and enhanced microwave admittance in otherwise paraelectric and insulating SrTiO3. Our work demonstrates that, with a well-defined termination, moiré reconstruction could serve as a route to emergent electrical behavior in twisted perovskite oxides.