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Robust Interlayer-Coherent Quantum Hall States in Twisted Bilayer Graphene.
Dohun Kim1, Byungmin Kang2,3, Yong-Bin Choi4
1Department of Physics and Chemistry, Daegu Gyeongbuk Institute of Science and Technology (DGIST), Daegu 42988, Republic of Korea.
Nano Letters
|December 16, 2022
Summary
We developed a novel two-dimensional electronic system using twisted bilayer graphene for high-temperature excitonic condensation. This system exhibits interlayer coherence and quantum Hall states at the second Landau level, paving the way for new condensed matter physics research.
Area of Science:
- Condensed Matter Physics
- Materials Science
Background:
- Two-dimensional electronic systems are crucial for exploring exotic quantum phenomena.
- Excitonic condensates require strong interlayer interactions and suppressed tunneling, conditions challenging to achieve simultaneously.
Purpose of the Study:
- To introduce a novel material system for realizing interlayer-coherent excitonic condensates.
- To investigate quantum Hall states and phase transitions in twisted bilayer graphene with large twist angles.
Main Methods:
- Fabrication and characterization of twisted bilayer graphene with large twist angles.
- Experimental observation of quantum Hall states at the second Landau level.
- Phenomenological model calculations for theoretical validation.
Main Results:
- Demonstration of odd-integer quantum Hall states with interlayer coherence at N=1.
- Observation of energy gaps of ~1 K, significantly larger than in conventional materials.
- Experimental evidence of various quantum Hall phase transitions.
Conclusions:
- Twisted bilayer graphene with large twist angles provides an ideal platform for high-temperature excitonic condensation.
- The observed phenomena are consistent with theoretical models, validating the material system's potential.
- This work opens new avenues for exploring interlayer-coherent quantum states in two-dimensional materials.
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