Plasmons in realistic graphene/hexagonal boron nitride moir\'e patterns

TL;DR

This paper theoretically investigates how moiré superlattices in nearly aligned graphene on hBN influence plasmonic excitations, revealing asymmetries in plasmon dispersion due to band structure effects.

Contribution

It introduces a continuum-model approach based on ab initio calculations to analyze plasmon behavior in graphene/hBN moiré patterns, highlighting electron-hole asymmetry effects.

Findings

Asymmetry in plasmon dispersion between positive and negative chemical potentials.

Rich absorption spectrum across the secondary Dirac point gap.

Moiré pattern effects significantly alter plasmon properties.

Abstract

Van der Waals heterostructures employing graphene and hexagonal boron nitride (hBN) crystals have emerged as a promising platform for plasmonics thanks to the tunability of their collective modes with carrier density and record values for plasmonics figures of merit. In this Article we investigate theoretically the role of moir\'e-pattern superlattices in nearly aligned graphene on hBN by using continuum-model Hamiltonians derived from ab initio calculations. We calculate the system's energy loss function for a variety of chemical potential values that are accessible in gated devices. Our calculations reveal that the electron-hole asymmetry of the moir\'e bands leads to a remarkable asymmetry of the plasmon dispersion between positive and negative chemical potentials, showcasing the intricate band structure and rich absorption spectrum across the secondary Dirac point gap for the hole bands.