Charge transport through one-dimensional Moiré crystals.

Roméo Bonnet,Maria Luisa Della Rocca,Clément Barraud,Aurélien Lherbier,Philippe Lafarge,Jean-Christophe Charlier

doi:10.1038/srep19701

Abstract

Moiré superlattices were generated in two-dimensional (2D) van der Waals heterostructures and have revealed intriguing electronic structures. The appearance of mini-Dirac cones within the conduction and valence bands of graphene is one of the most striking among the new quantum features. A Moiré superstructure emerges when at least two periodic sub-structures superimpose. 2D Moiré patterns have been particularly investigated in stacked hexagonal 2D atomic lattices like twisted graphene layers and graphene deposited on hexagonal boron-nitride. In this letter, we report both experimentally and theoretically evidence of superlattices physics in transport properties of one-dimensional (1D) Moiré crystals. Rolling-up few layers of graphene to form a multiwall carbon nanotube adds boundaries conditions that can be translated into interference fringes-like Moiré patterns along the circumference of the cylinder. Such a 1D Moiré crystal exhibits a complex 1D multiple bands structure with clear and robust interband quantum transitions due to the presence of mini-Dirac points and pseudo-gaps. Our devices consist in a very large diameter (>80 nm) multiwall carbon nanotubes of high quality, electrically connected by metallic electrodes acting as charge reservoirs. Conductance measurements reveal the presence of van Hove singularities assigned to 1D Moiré superlattice effect and illustrated by electronic structure calculations.

Highlights

Only the outermost shells are carrying the current in the device due to a large intershell resistance
This lateral distortion caused by closed curved surface can be combined with a twist of the walls corresponding to different tube chiralities, inducing another type of 2D Moiré pattern
Superlattice Dirac zero. (c) Conductance point measurement performed at 4.2K on sample A with highly resistive contacts. van Hove singularities are marked with ◊ and conductance oscillations due to intershell interactions are marked with ♦ . (d) Simulated density of states (DOS) and ballistic conductance of the triple-wall CNT (TWCNT) presented in panel (b)

Summary

Introduction

Only the outermost shells are carrying the current in the device due to a large intershell resistance. The simulations of the DOS and ballistic conductance (G) for a zigzag TWCNT (same configuration as in Fig. 2b) give a better physical insight (see Fig. 2d) as they reproduce qualitatively the main features measured experimentally in the pseudo-gap regime (Fig. 2b).

Results

Conclusion