Universal superlattice potential for 2D materials from twisted interface inside h-BN substrate

TL;DR

This paper proposes a universal, non-invasive method to create superlattice potentials in 2D materials using patterned electrical polarization in h-BN substrates, demonstrated through first-principles calculations.

Contribution

It introduces a novel approach leveraging patterned polarization in h-BN to generate superlattice potentials in various 2D materials without invasive techniques.

Findings

Potential strength up to 200 meV can be achieved.

Superlattice potential is tunable via vertical distance.

Out-of-plane electric field enables new excitonic phenomena.

Abstract

Lateral superlattices in 2D materials are emerging as a powerful platform for exploring novel quantum phenomena, which can be realized through the proximity coupling in forming moir\'e pattern with another layer. This approach, however, is invasive, material-specific, and requires small lattice mismatch and suitable band alignment, largely limited to graphene and transition metal dichalcogenides (TMDs). Hexagonal boron nitride (h-BN) of anti-parallel (AA') stacking order has been an indispensable building block, as dielectric substrates and capping layers for realizing high quality van der Waals devices. There is also emerging interest on parallelly aligned h-BN of Bernal (AB) stacking, where the broken inversion and mirror symmetries lead to out-of-plane electrical polarization with sign controlled by interlayer translation. Here we show that the laterally patterned electrical polarization at a nearly parallel interface within the h-BN substrate or capping layer can be exploited to create non-invasively a universal superlattice potential in general 2D materials. The feasibility is demonstrated by first principle calculations for monolayer MoSe2, black phosphorus, and antiferromagnetic MnPSe3 on such h-BN substrate. The potential strength can reach 200 meV, customizable in this range through choice of vertical distance of target material from the interface in h-BN. We also find sizable out-of-plane electric field at the h-BN surface, which can realize superlattice potential for interlayer excitons in TMD bilayers as well as dipolar molecules. The idea is further generalized to AB stacked h-BN film subject to torsion with adjacent layers all twisted with an angle, which allows the potential and field strength to be scaled up with film thickness, saturating to a quasi-periodic one with chiral structure.