Moire Superlattice Modulations in Single-Unit-Cell FeTe Films Grown on NbSe2 Single Crystals

TL;DR

This study investigates moire superlattice patterns in single-unit-cell FeTe films grown on NbSe2 substrates, revealing their atomic sharpness and the origins of their electronic or structural nature depending on misorientation angles.

Contribution

It demonstrates the formation of moire superlattices in FeTe/NbSe2 heterostructures and distinguishes their electronic and structural origins based on misorientation angles.

Findings

Moire patterns observed in FeTe films on NbSe2.

Superlattice modulations have electronic origin at small angles.

Structural relaxation dominates at larger misorientation angles.

Abstract

Interface can be a fertile ground for exotic quantum states, including topological superconductivity, Majorana mode, fractal quantum Hall effect, unconventional superconductivity, Mott insulator, etc. Here we grow single-unit-cell (1UC) FeTe film on NbSe2 single crystal by molecular beam epitaxy (MBE) and investigate the film in-situ with home-made cryogenic scanning tunneling microscopy (STM) and non-contact atomic force microscopy (AFM) combined system. We find different stripe-like superlattice modulations on grown FeTe film with different misorientation angles with respect to NbSe2 substrate. We show that these stripe-like superlattice modulations can be understood as moire pattern forming between FeTe film and NbSe2 substrate. Our results indicate that the interface between FeTe and NbSe2 is atomically sharp. By STM-AFM combined measurement, we suggest the moire superlattice modulations have an electronic origin when the misorientation angle is relatively small (<= 3 degree) and have structural relaxation when the misorientation angle is relatively large (>= 10 degree).