Moiré Engineering of Cooper-Pair Density Modulation States

Cooper-pair density modulation (CPDM) states are superconducting phases in which the order parameter varies periodically in real space, typically associated with translational or sublattice symmetry breaking. In this work, we demonstrate moiré-induced CPDM states in a bilayer heterostructure formed by epitaxially stacking one quintuple layer (1 QL) of topological insulator Sb₂Te₃ on a six unit cell (6 UC) antiferromagnetic FeTe layer. Scanning tunneling microscopy and spectroscopy (STM/S) measurements reveal a moiré superlattice formed between the hexagonal Te lattice of Sb₂Te₃ and the square Te lattice of FeTe, which spatially modulates the two superconducting gaps of the 1 QL Sb₂Te₃/6 UC FeTe bilayer. Our Josephson STM/S measurements provide direct real-space imaging of the CPDM states with a wavelength corresponding to the periodicity of the moiré superlattice. By substituting Sb₂Te₃ with Bi₂Te₃, we achieve control over both the periodicity and magnitude of the CPDM states. Our work demonstrates an epitaxial strategy for synthesizing wafer-scale moiré superlattices from materials with different crystal symmetries and reveals a new mechanism for engineering CPDM states in designer bilayer heterostructures.