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Twisted Trilayer Graphene: A Precisely Tunable Platform for Correlated Electrons
Ziyan Zhu1, Stephen Carr1, Daniel Massatt2
1Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA.
Physical Review Letters
|September 25, 2020
Summary
We developed a new model for twisted trilayer graphene (tTLG) to precisely tune electronic coupling. This system reveals magic angles where van Hove singularities (VHS) merge, enhancing correlated behaviors in materials.
Area of Science:
- Condensed Matter Physics
- Materials Science
- Quantum Mechanics
Background:
- Twisted bilayer graphene (TBG) shows correlated behaviors linked to van Hove singularities (VHS).
- Precise tuning of electronic interlayer coupling is key to maximizing correlated phenomena.
- Twisted trilayer graphene (tTLG) offers a tunable platform for studying these effects.
Purpose of the Study:
- To introduce twisted trilayer graphene (tTLG) with two independent twist angles as a tunable system.
- To explore the evolution of van Hove singularities (VHS) in the twist-angle phase space of tTLG.
- To develop a general low-energy electronic structure model for tTLG.
Main Methods:
- Development of a general low-energy electronic structure model for tTLG.
- Analysis of the model's infinite-dimensional basis and lack of a Brillouin zone.
- Investigation of VHS evolution across the twist-angle phase space.
Main Results:
- Demonstration of a wide range of magic angles in tTLG where VHS merge.
- Observation of sharp peaks in the density of states at the charge-neutrality point.
- Identification of two distinct mechanisms leading to these peaks: incommensurate perturbation and bilayer moiré hybridization.
Conclusions:
- tTLG is an ideal system for precisely tuning electronic interlayer coupling and correlated behaviors.
- The developed model provides insights into the complex electronic structure and VHS phenomena in tTLG.
- Magic angles and hybridization mechanisms offer new pathways for engineering correlated states in moiré materials.
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