Absorptive pinhole collimators for ballistic Dirac fermions in graphene

摘要

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