Moire Engineering of Cooper-Pair Density Modulation States

TL;DR

This study demonstrates how moire superlattices in layered heterostructures can be used to engineer and control Cooper-pair density modulation states in superconductors.

Contribution

It introduces an epitaxial method to create moire superlattices from materials with different symmetries, enabling control over CPDM states.

Findings

Moiré superlattices modulate superconducting gaps in bilayer heterostructures.

STM/S imaging reveals real-space CPDM states with moire periodicity.

Substituting materials tunes the periodicity and magnitude of CPDM states.

Abstract

Cooper-pair density modulation (CPDM) states are superconducting phases in which the order parameter varies periodically in real space without breaking translational symmetry. Recently, moire superlattices in layered materials have emerged as powerful platforms for engineering charge density with tunable lattice symmetry, offering a new route to creating and controlling CPDM states. In this work, we demonstrate moire-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 moir\'e 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 moire 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 moire superlattices from materials with different crystal symmetries and reveals a new mechanism for engineering CPDM states in designer bilayer heterostructures.