Quantum optics of electrons in graphene

Abstract

The unique properties of graphene's band structure can lead to negative refraction of charge carriers incident on PN junctions. When coupled with an angular dependent transmission probability this can be utilised to form a novel split path interferometer. Many practical challenges are present and novel methods of fabrication are required to realise such a device. A large mean free path is required in order to achieve ballistic transport; a fundamental requirement of such a lensing device. Graphene on a hexagonal boron nitride (hBN) substrate is used in order to remove as many scattering sites as possible to enable the devices to be modelled using ballistic transport. Bubbles between graphene and boron nitride flakes are found and a method for their removal explained. Equipment was modified to allow the use of the latest graphene flake dry transfer methods, which enable the fabrication of hBN-graphene-hBN sandwich devices with one dimensional edge contacts. Multiple device designs are proposed which would exhibit interesting physics and give evidence for negative refraction in graphene and for the angular transmission probability of Klein tunnelling. The possibility of using He ion carving to produce a very small quantum point contact was explored and a nanoribbon with a width of 8 nm was fabricated and measured.

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Identifiers

ORCID for Hendrik Ulbricht: orcid.org/0000-0003-0356-0065

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