Moir\'e-induced bandgap tuning by varying electric dipole in InSe/CuSe vertical heterostructure

TL;DR

This study investigates how moiré patterns in InSe/CuSe heterostructures, created by lattice mismatch and twist angles, can modulate electronic properties, especially the bandgap, through combined experimental and theoretical approaches.

Contribution

It demonstrates that moiré-induced electric dipoles and charge transfer can tune the bandgap and electronic features in InSe/CuSe heterostructures, revealing new mechanisms for electronic property control.

Findings

Moiré pattern with ~3.48nm periodicity and 11° twist angle observed.

Bandgap variation of 400 meV across different stacking sites.

Moiré-induced electric dipole is key to bandgap tuning.

Abstract

The stacked two layered materials with a lattice constant mismatch and/or with twist angle relative to each other can create a moir\'e pattern, modulating the electronic properties of the pristine materials. Here, we combine scanning tunneling microscopy/spectroscopy and density functional theory calculations to investigate the moir\'e potential induced bandgap tuning in InSe/CuSe vertical heterostructure synthesized by a two-step of molecular beam epitaxy. Scanning tunneling microscopy measurements demonstrate the heterostructure with a superlattice periodicity of ~3.48nm and a twist angle of about 11{\deg} between the monolayers. Scanning tunneling spectroscopy record on the different stacking sites of the heterostructure reveals the bandgap of the InSe is location-dependent and a variation of 400 meV is observed. Density functional theory calculations reveal that the moir\'e-induce electric dipole in the monolayer InSe is the key factor for tuning the bandgap. Besides, charge transfer between CuSe and InSe also contributes to the bandgap variation due to its stacking related. We also show that the moir\'e potential not only can tune the bandgap of InSe but also can vanish the Dirac nodal line of CuSe in some stackings. Our explorations provide valuable information in understanding the electronic properties of the twodimensional moir\'e materials.