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Optimized Fabrication Procedure for High-Quality Graphene-based Moiré Superlattice Devices
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Helical Edge States and Quantum Phase Transitions in Tetralayer Graphene
Shi Che1, Yanmeng Shi2, Jiawei Yang1
1Department of Physics, The Ohio State University, Columbus, Ohio 43210, USA.
Physical Review Letters
|August 4, 2020
Summary
Researchers observed two distinct topological phases in charge neutral tetralayer graphene, revealing helical edge states crucial for Majorana fermions. This finding advances understanding of complex quantum phases in few-layer graphene systems.
Area of Science:
- Condensed Matter Physics
- Materials Science
- Quantum Physics
Background:
- Helical conductors exhibiting spin-momentum locking are key for realizing Majorana fermions.
- Few-layer graphene offers a tunable platform for exploring exotic quantum phenomena.
Purpose of the Study:
- To investigate topological phases and helical edge states in charge neutral Bernal-stacked tetralayer graphene.
- To map the phase diagram and understand the underlying mechanisms governing transitions.
Main Methods:
- Fabrication of tetralayer graphene in Hall bar and Corbino geometries.
- Application of perpendicular magnetic fields (B⊥) and out-of-plane displacement fields (D).
- Electrical transport measurements to observe conductance and phase transitions.
Main Results:
- Observation of a phase diagram with insulating and two metallic phases.
- Identification of 0, 1, and 2 helical edge states corresponding to the observed phases.
- A theoretical model successfully explained conductance plateaus and phase transitions.
Conclusions:
- Two topologically distinct phases with helical edge states were identified in tetralayer graphene.
- Phase transitions are driven by competing interlayer hopping, electrostatic, and exchange interactions.
- This work underscores the rich quantum phases and competing symmetries in few-layer graphene.
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