Multiple negative differential conductance regions and inelastic phonon assisted tunneling in graphene-hBN-graphene structures

TL;DR

This paper investigates how the rotational alignment in graphene-hBN-graphene devices causes multiple negative differential conductance regions and how phonon-assisted inelastic tunneling produces sharp features in the current-voltage characteristics.

Contribution

It provides a detailed analysis of the impact of lattice alignment and phonon interactions on tunneling behavior in graphene-based heterostructures, revealing new conductance phenomena.

Findings

Multiple negative differential conductance regions due to lattice alignment.

Sharp peaks in current derivatives from phonon-assisted inelastic tunneling.

Dependence of tunneling features on rotational angles and phonon interactions.

Abstract

In this paper we study in detail the effect of the rotational alignment between a hexagonal boron nitride (hBN) slab and the graphene layers in the vertical current of a a graphene-hBN-graphene device. We show how for small rotational angles, the transference of momentum by the hBN crystal lattice leads to multiple peaks in the I-V curve of the device, giving origin to multiple regions displaying negative differential conductance. We also study the effect of scattering by phonons in the vertical current an see how the opening up of inelastic tunneling events allowed by spontaneous emission of optical phonons leads to sharp peaks in the second derivative of the current.