University of Minnesota researcher recognized for seminal work on electronic properties of twisted bilayer graphene, a novel 2D material
MELVILLE, NY, October 2, 2024 — Dr. Alexander Watson, Assistant Professor of Mathematics at the University of Minnesota, has been selected to receive the 2023 Journal of Mathematical Physics Young Researcher Award.
The award recognizes Watson’s contributions to “Bistritzer-MacDonald dynamics in twisted bilayer graphene,” which he co-authored with Tianyu Kong, Allan H. MacDonald, and Mitchell Luskin. The paper appeared in AIP Publishing’s Journal of Mathematical Physics (JMP) in March 2023.
“Winning this award is a great honor, especially looking at the list of previous winners and considering the many outstanding papers published by young investigators in JMP,” said Dr. Watson. “I will take it as encouragement to continue working hard at the interface of mathematics with physics.”
Dr. Watson’s research utilizes mathematical theory to understand how fundamental theoretical models can be used to predict the properties of a given material — and seeks specifically to simplify those models while still accurately describing the full breadth of the material’s properties. In recent years, he has turned his attention to stacked two-dimensional materials like twisted bilayer graphene, where these simplified models can pick up the slack when fundamental modeling falls short.
Discovered in 2004, graphene is a versatile two-dimensional material composed of carbon atoms arranged in a honeycomb lattice. It is remarkably light and strong. It also conducts heat and electricity extraordinarily well. Since its discovery, researchers have worked to understand the dynamics behind its function.
In 2011, Rafi Bistritzer and Allan H. MacDonald correctly predicted that stacking two layers of graphene on top of each other in a certain orientation would dramatically alter the material’s electronic properties. The model they based their prediction on is now known as the Bistritzer-MacDonald model.
“Our paper showed that there exist conditions under which the Bistritzer-MacDonald model can be rigorously proved to control the dynamics of a more fundamental ‘tight-binding’ model of twisted bilayer graphene,” said Dr. Watson, noting his team’s proof captures an “important and subtle” effect where momentum space-hopping in the underlying model is much shorter range than would be expected because of the finite spacing between the graphene layers. He also stressed that the conditions specified by his team are physically reasonable and measurable by experiment.
“We are excited to showcase Dr. Watson’s groundbreaking research on the electronic properties of twisted bilayer graphene and two-dimensional moiré materials,” said JMP Editor-in-Chief Jan Philip Solovej, PhD. “There is great interest in this topic throughout the physics community. It has important applications in bioengineering, composite materials, energy technology, nanotechnology, and numerous other disciplines.”
According to Dr. Watson, there are a number of open questions he and his team hope to answer in the wake of this paper. For example, they are currently working to understand corrections to the Bistritzer-MacDonald model and how those corrections might break symmetries of the original model.
“I am also currently working on deriving effective models of twisted bilayer graphene when our assumptions do not hold, in order to better understand exactly why the regime we identify is so special,” Dr. Watson said. Further work includes the derivation of effective models of other two-dimensional materials, especially the transition metal dichalcogenides.
A native of London, England, Dr. Watson completed his PhD in Applied Mathematics at Columbia University under the supervision of Michael Weinstein. He subsequently held postdoctoral positions at Duke University and the University of Minnesota before joining the faculty of the University of Minnesota in 2023 as an assistant professor of mathematics.
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