Absorptive pinhole collimators for ballistic Dirac fermions in graphene

TL;DR

This paper introduces a novel method to generate highly collimated electron beams in graphene using absorptive pinhole collimators, enabling precise control of ballistic Dirac fermions for advanced electron-optical applications.

Contribution

The authors develop a new collimation technique in graphene employing absorptive pinhole collimators, overcoming chiral transport limitations for electron-optical device design.

Findings

Achieved electron beams with angular width 18 degrees or narrower.

Transmission matches semiclassical predictions.

Demonstrated effective collimation in high-mobility graphene.

Abstract

Ballistic electrons in solids can have mean free paths far larger than the smallest features patterned by lithography. This has allowed development and study of solid-state electron-optical devices such as beam splitters and quantum point contacts, which have informed our understanding of electron flow and interactions. Recently, high-mobility graphene has emerged as an ideal two-dimensional semimetal that hosts unique chiral electron-optical effects due to its honeycomb crystalline lattice. However, this chiral transport prevents simple use of electrostatic gates to define electron-optical devices in graphene. Here, we present a method of creating highly-collimated electron beams in graphene based on collinear pairs of slits, with absorptive sidewalls between the slits. By this method, we achieve beams with angular width 18 degrees or narrower, and transmission matching semiclassical predictions.