Physics of graphene/hexagonal boron nitride heterostructures

At the foundation of electronics lies the observation that energies of electrons travelling in materials with regular, periodic arrangement of atoms are quantized and restricted to electronic bands. This way, depending on the arrangement of those bands and experimental conditions, some materials conduct and some are insulating. At the same time, we know that another quantizing restriction on the energy of a travelling charged particle can be imposed with magnetic field. Very interesting physics has been predicted for the situation in which those two effects compete with similar strength and the formation of bands interplays with that of magnetic levels, leading to a self-repetitive pattern bearing likeness to self-similar patterns on leaves or those formed by snowflakes. Unfortunately, such electronic band structure patterns remained elusive due to the conditions on the periodicity of the system and magnetic field that need to be fulfilled simultaneously. Recently, it has been shown that the electronic band structure in sandwiches made of graphene and hexagonal boron nitride, two atomically thin materials, becomes such a self-similar pattern. This is because, apart from regular arrangement of atoms within each of the materials, another periodicity known as moiré arises due to complicated overlay between the two atomic layers and can be probed thanks to the outstanding quality of those materials. In this project, I will investigate the electronic properties of graphene/hexagonal boron nitride systems in order to understand the interplay between periodicity and magnetic field quantizations in those structures. I will explore theoretically the result of manipulating the latter by rearranging the layers with respect to each other and suggest what experimental tools give the fullest knowledge of the physics at play. Finally, I will model the self-similar electronic band structure formed in external magnetic field and explore the fascinating physics it is describing.

This proposal explores the physics at the crossroads between the band theory of solids and quantizing effects of a magnetic field on a charged quantum particle. As such, its main impact will come through contributing to the fundamental knowledge we have about the electronic properties of systems pushed into this regime. This impact will be realised by publishing all results in peer-reviewed scientific journals and free-access repositories, in order to disseminate them in the academic community. At the same time, to share the knowledge gained during my research with the general public, I will work together with the University of Bath press office on publicising my results in news releases, as well as build a dedicated webpage.

Because the graphene/hexagonal boron nitride structures show promise with regards to electronic applications, the detailed material knowledge gained during the project will also be useful to the broader community of material technologists. To increase this impact of my work, I will address the properties of graphene/hexagonal boron nitride structures as investigated with the most relevant material characterization techniques used by the industry. I will also disseminate my results in journals targeting semiconductor technology community and attend appropriate conferences in the UK and abroad. Most importantly, in order to maximise the impact of the theoretical models constructed in this project, alongside my research I have planned multiple visits to National Graphene Institute in Manchester and a three-month visit to the Graphene Research Centre in Singapore. Both these institutions address progress in the field of two-dimensional crystals holistically, combining theoretical and experimental research with a more applied approach oriented on new technologies. Presenting my results at and through those institutions will significantly contribute to generating impact for my research.