From moiré superlattices to twistronic solids

The University of Bath is inviting applications for the following PhD project under the supervision Dr Marcin Mucha-Kruczynski and Dr Simon Crampin in the Department of Physics.

Overview of the Project:

Since the isolation of graphene in 2004, many other layered materials have been realised in the single layer limit of two-dimensional (2D) crystals. These atomically thin materials span virtually all classes of properties, from insulators to metals, magnets to superconductors. Moreover, because interaction between the layers is van der Waals (vdW) in nature and does not involve direct chemical bonds, any two layered crystals can be put on top of one another to form an atomically sharp interface without the normal constraints lattice constant matching or mutual orientation of crystallographic directions. For a general angle between the 2D primitive vectors of neighbouring materials, beating of the associated lattice periodicities leads to the formation of a quasi-periodic moiré superlattice which provides a new source of Bragg scattering at the interface. In stacks of 2D crystals, moiré can significantly affect properties of the stack and has in recent years led to the discovery of novel phenomena like the observation of Hofstadter’s butterfly [1] in graphene on hexagonal boron nitride and the appearance of correlated electronic phases [2] in magic-angle twisted bilayer graphene.

In this project, you will aim to answer the question how moiré superlattice physics can be utilised in vdW solids, in which twisted interfaces are embedded in bulk materials. This work is challenging and requires novel theoretical tools because the cornerstone of solid state physics, Bloch’s theorem, cannot be applied: (i) for a general twist between layers the moiré is incommensurate with the in-plane lattices; (ii) an interface between half crystals locally disrupts translational periodicity in the normal direction. You will determine the conditions necessary for the survival of the moiré-induced effects in truly three-dimensional structures and explore phenomena associated with twisted interfaces in close proximity. In doing so, you will establish a route to preserve and exploit the rich physics of 2D Flatland in the 3D Spaceland.

The supervisory team brings expertise in modelling twisted interfaces and moiré superlattices (Mucha-Kruczynski) [1, 2-4] and modelling semi-infinite substrates and interfacial states (Crampin) [5-6]. You will also be interacting with experimental and theoretical collaborators from the UK and abroad.

Project keywords: Two-dimensional materials, moiré superlattices, graphene, graphite.

Candidate Requirements:

The successful candidate should hold, or expect to receive, a first class or good 2.1 Master’s degree (or equivalent) in Physics (Theoretical Physics preferred) or Theoretical/Quantum Chemistry (or other closely related field). A keen interest in theoretical condensed matter physics and a strong work ethic are essential. Also required is basic programming experience (knowledge of Matlab/Mathematica will be beneficial but is not necessary).

Non-UK applicants must meet our English language entry requirement.

Enquiries and Applications:

Informal enquiries are welcomed and should be directed to Dr Marcin Mucha-Kruczynski (email [Email Address Removed]).

Formal applications should be made via the University of Bath’s online application form for a PhD in Physics.

More information about applying for a PhD at Bath may be found on our website.

Equality, Diversity and Incusion:

We value a diverse research environment and aim to be an inclusive university, where difference is celebrated and respected. We welcome and encourage applications from under-represented groups.

If you have circumstances that you feel we should be aware of that have affected your educational attainment, then please feel free to tell us about it in your application form. The best way to do this is a short paragraph at the end of your personal statement.