# Design of graphene waveguide: Effect of edge orientation and waveguide configuration

## TL;DR

This paper provides a comprehensive theoretical analysis of graphene waveguides, examining how edge orientation and configuration affect electron transport, conductance properties, and potential applications in ballistic integrated circuits.

## Contribution

It introduces a detailed study of conductance in graphene waveguides with different edge orientations and configurations, including bent shapes, using Green's function and tight-binding models.

## Key findings

- Conductance plateaus at 4e^2/h observed in both armchair and zigzag orientations.
- Zigzag waveguides show wider first quantized conductance plateau.
- Edge orientation and geometry significantly influence conductance profiles.

## Abstract

Electron transport in a graphene quantum well can be analogous to photon transmission in an optical fiber. In this work, we present a detailed theoretical analysis to study the transport characteristics of graphene waveguides under the influence of different edge orientations. Non-equilibrium Green's function approach in combination with tight-binding Hamiltonian has been utilized to investigate the conductance properties of straight armchair and zigzag oriented graphene waveguides. Conductance plateaus at integer steps of $4e^2/h$ have been observed in both orientations while the zigzag oriented waveguides present a wider first quantized plateau compared to that in the armchair oriented ones. Using various geometric and physical parameters, including side-barrier and waveguide width, and the metallic properties of terminals, we investigate the conductance profile of waveguides. In addition to the observation of valley-symmetry in both edge orientations, this article explores the critical influence of drain contacts on waveguide conductance. Furthermore, we extended our transport study to three different highly bent waveguide configurations, such as U-shape, L-shape and split-shape waveguides, in order to explore their applications in graphene-based ballistic integrated circuit devices. In the end, we also calculated the conductance of larger graphene waveguides using the scalable tight-binding model, in order to compare the results obtained from the original model.