Condensed Matter Theory Seminar - Fedor Popov - Simons Center/Stony Brook University

Event time: 
Thursday, September 12, 2024 - 2:30pm to 3:30pm
Location: 
Sloane Physics Laboratory (SLP), Room 63 See map
217 Prospect Street
New Haven, CT 06511
Event description: 

“Magic Angles in Twisted Multilayer Graphene”

We consider a configuration of three stacked graphene monolayers with equal consecutive twist angles θ. Remarkably, in the chiral limit when interlayer coupling terms between AA sites of the moir ́e pattern are neglected we find four perfectly flat bands (for each valley) at a sequence of magic angles which are exactly equal to the twisted bilayer graphene (TBG) magic angles divided by 2. Therefore, the first magic angle for equal-twist trilayer graphene (eTTG) in the chiral limit is θ∗ ≈ 1.05◦/√2 ≈ 0.74◦. We prove this relation analytically and show that the Bloch states of the eTTG’s flat bands are non-linearly related to those of TBG’s. Additionally, we show that at the magic angles, the upper and lower bands must touch the four exactly flat bands at the Dirac point of the middle graphene layer. Finally, we explore the eTTG’s spectrum away from the chiral limit through numerical analysis.