Resonant interlayer coupling in NbSe$_2$-graphite epitaxial moir{\'e} superlattices

TL;DR

This study demonstrates the formation of moiré superlattices in epitaxial NbSe₂ on graphite, revealing interlayer coupling effects that influence charge-density wave behavior and offering new avenues for quantum material engineering.

Contribution

It provides the first spectroscopic evidence of moiré lattice formation in epitaxial NbSe₂-graphite heterostructures, combining experimental measurements with theoretical analysis.

Findings

Moiré replicas of graphite π states form interlocking Dirac cones.

Interlayer coupling affects charge-density wave properties.

Moiré engineering can control collective states in 2D materials.

Abstract

Moir{\'e} heterostructures, created by stacking two-dimensional (2D) materials together with a finite lattice mismatch or rotational twist, represent a new frontier of designer quantum materials. Typically, however, this requires the painstaking manual assembly of heterostructures formed from exfoliated materials. Here, we observe clear spectroscopic signatures of moir{\'e} lattice formation in epitaxial heterostructures of monolayer (ML) NbSe$_2$ grown on graphite substrates. Our angle-resolved photoemission measurements and theoretical calculations of the resulting electronic structure reveal moir{\'e} replicas of the graphite $\pi$ states forming pairs of interlocking Dirac cones. Interestingly, these intersect the NbSe$_2$ Fermi surface at the $\mathbf{k}$-space locations where NbSe$_2$'s charge-density wave (CDW) gap is maximal in the bulk. This provides a natural route to understand the lack of CDW enhancement for ML-NbSe$_2$/graphene as compared to a more than four-fold enhancement for NbSe$_2$ on insulating support substrates, and opens new prospects for using moir{\'e} engineering for controlling the collective states of 2D materials.