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Topological flat bands in twisted trilayer graphene
Zhen Ma1, Shuai Li1, Ya-Wen Zheng1
1School of Physics and Wuhan National High Magnetic Field Center, Huazhong University of Science and Technology, Wuhan 430074, China.
Twisted trilayer graphene (TLG) exhibits flat bands with nontrivial topology. Its unique band structure, tunable by twist angle and electric fields, makes it a promising platform for studying correlated physics.
Area of Science:
- Condensed Matter Physics
- Materials Science
- Quantum Mechanics
Background:
- Twisted bilayer graphene (TBG) has shown unique electronic properties due to flat bands.
- Topological flat bands are crucial for understanding novel quantum phenomena.
- Simpler systems with similar properties are sought for experimental exploration.
Purpose of the Study:
- To comprehensively calculate the band structures and band topology of twisted trilayer graphene (TLG).
- To investigate the influence of twist angle and electric fields on TLG's band topology.
- To establish TLG as a potential experimental platform for topological flat band physics.
Main Methods:
- Utilizing a continuum model for comprehensive band structure calculations.
- Analyzing the valley Chern number of nearly flat bands.
- Investigating the effect of perpendicular electric fields on band gaps.
Main Results:
- Identified a magic angle of approximately 1.12° for twisted TLG, revealing two nearly flat bands.
- Observed that small twist angles induce tunable gaps at Dirac points, further enhanced by electric fields.
- Demonstrated that valley Chern numbers are dependent on twist angle and electric field strength.
Conclusions:
- Twisted trilayer graphene presents a tunable topological flat band system.
- Its reduced symmetry offers a distinct platform compared to TBG and twisted double bilayer graphene for correlated states.
- TLG is proposed as an ideal experimental system for exploring strongly correlated physics in nontrivial topological flat bands.
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