Effects of Interlayer Coupling on Hot Carrier Dynamics in Graphene-derived van der Waals Heterostructures

TL;DR

This study uses ab initio calculations to analyze how interlayer coupling affects hot carrier lifetimes in graphene-based heterostructures, revealing ways to optimize materials for plasmonic applications.

Contribution

It provides a detailed analysis of electron scattering mechanisms in graphene heterostructures, highlighting how interlayer interactions influence hot carrier dynamics.

Findings

High carrier lifetimes (~3 ps) in graphene are reduced in graphite but enhanced in heterostructures.

Carrier lifetimes decrease rapidly with increasing energy, becoming shorter than noble metals above 0.5 eV.

Spacer layer properties like high dielectric constant and heavy atoms can improve hot carrier transport.

Abstract

Graphene exhibits promise as a plasmonic material with high mode confinement that could enable efficient hot carrier extraction. We investigate the lifetimes and mean free paths of energetic carriers in free-standing graphene, graphite and a heterostructure consisting of alternating graphene and hexagonal boron nitride layers using ab initio calculations of electron-electron and electron-phonon scattering in these materials. We find that the extremely high lifetimes (3 ps) of low-energy carriers near the Dirac point in graphene, which are a hundred times larger than that in noble metals, are reduced by an order of magnitude due to inter-layer coupling in graphite, but enhanced in the heterostructure due to phonon mode clamping. However, these lifetimes drop precipitously with increasing carrier energy, and are smaller than those in noble metals at energies exceeding 0.5 eV. By analysing the contribution of different scattering mechanisms and inter-layer interactions, we identify desirable spacer layer characteristics - high dielectric constant and heavy atoms - that could pave the way for plasmonic heterostructures with improved hot carrier transport.