Quantum-Confined Electronic States arising from Moir\'e Pattern of MoS2-WSe2 Hetero-bilayers

TL;DR

This study investigates moiré pattern-induced quantum-confined electronic states in MoS2-WSe2 hetero-bilayers using STM/STS, revealing temperature-dependent spectral features and wave function structures.

Contribution

It provides direct experimental evidence of quantum-confined states within moiré patterns in 2D hetero-bilayers, highlighting temperature effects on spectral sharpness and wave function mapping.

Findings

Sharp spectral peaks at 5 K indicate quantum confinement.

Moiré pattern causes energy shifts in tunneling spectra.

Temperature influences the visibility of confined states.

Abstract

A two-dimensional (2D) hetero-bilayer system consisting of MoS2 on WSe2, deposited on epitaxial graphene, is studied by scanning tunneling microscopy and spectroscopy at temperatures of 5 and 80 K. A moir\'e pattern is observed, arising from lattice mismatch of 3.7% between the MoS2 and WSe2. Significant energy shifts are observed in tunneling spectra observed at the maxima of the moir\'e corrugation, as compared with spectra obtained at corrugation minima, consistent with prior work. Furthermore, at the minima of the moir\'e corrugation, sharp peaks in the spectra at energies near the band edges are observed, for spectra acquired at 5 K. The peaks correspond to discrete states that are confined within the moir\'e unit cells. Conductance mapping is employed to reveal the detailed structure of the wave functions of the states. For measurements at 80 K, the sharp peaks in the spectra are absent, and conductance maps of the band edges reveal little structure.