Steve Simon (Oxford U)“Kekule spirals in twisted bilayer graphene”

Steve Simon (Oxford U)
Talk given at Condensed Matter in the City, July 14th, 2023.
“Kekule spirals in twisted bilayer graphene”
Abstract: I review some of the puzzles of the phase diagram of magic angle twisted bilayer graphene. I discuss first the so-called "strong coupling" or "flat band limit". While this describes some of the experiments, we find that there are still a number of experimental features that are not obtained correctly. In a more realistic calculation, keeping some experimentally relevant deviations from the flat-band limit, we find a new type of order which we dub "Incommensurate Kekule Spiral." This result appears to be in agreement with a very large number of experimental observations and has now been directly observed in STM experiment.