Manipulation of edge states in microwave artificial graphene

Matthieu Bellec,Fabrice Mortessagne,Ulrich Kuhl,Gilles Montambaux

doi:10.1088/1367-2630/16/11/113023

Abstract

Edge states are an important ingredient in understanding transport properties of graphene nanoribbons. We study experimentally the existence and the internal structure of edge states under uniaxial strain of the three main edges: zigzag, bearded, and armchair. The experiments are performed on artificial microwave graphene flakes, where the wavefunctions are obtained by direct imaging. We show that uniaxial strain can be used to manipulate the edge states: a single parameter controls their existence and their spatial extension into the ribbon. By combining a tight-binding approach and topological arguments, we provide an accurate description of our experimental findings. A new type of zero-energy state appearing at the intersection of two edges, namely the corner state, is also observed and discussed.

Highlights

Edge states play an essential role in condensed matter physics for both fundamental aspects and electronic transport applications
We propose an experimental manipulation of edge state properties by controlling a uniaxial strain
We show experimentally how uniaxial strain acts as a switch between zigzag and bearded edge states

Summary

Introduction

Edge states play an essential role in condensed matter physics for both fundamental aspects and electronic transport applications. Not strictly speaking topologically protected, edge states in graphene possess a topological origin coined by the Zak phase and remain robust against weak chiral symmetry perturbations [11, 12]. These peculiar features are due to the multicomponent (spinorial) structure of the wavefunction. We propose an experimental manipulation of edge state properties by controlling a uniaxial strain. The existence of a new type of states, appearing at the intersection of two type of edges, namely corner states, is eventually discussed

Zigzag and bearded edges in honeycomb lattice under uniaxial strain

Zak phase

Study of armchair edges in honeycomb lattice under uniaxial strain

Conclusion