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11:42
Fabrication of Gate-tunable Graphene Devices for Scanning Tunneling Microscopy Studies with Coulomb Impurities
Published on: July 24, 2015
Spontaneously gapped ground state in suspended bilayer graphene
Physical Review Letters
|March 10, 2012
Summary
Researchers studied electrical transport in suspended bilayer graphene, discovering two distinct behaviors. Some samples showed an insulating quantum-Hall state, while others exhibited a spontaneously broken symmetry state with compressible edge states.
Area of Science:
- Condensed Matter Physics
- Materials Science
Background:
- Bilayer graphene exhibits an eightfold degeneracy due to spin, valley, and layer symmetry.
- This degeneracy allows for various broken symmetry states induced by external fields or interactions.
Purpose of the Study:
- Investigate electrical transport properties of clean, current-annealed, suspended bilayer graphene.
- Characterize different broken symmetry states in bilayer graphene.
Main Methods:
- Fabrication of suspended bilayer graphene devices using current annealing.
- Electrical transport measurements, including differential conductance, under varying magnetic fields.
- Analysis of Landau level behavior and conductance characteristics.
Main Results:
- Two types of devices (B1 and B2) were identified based on their transport properties.
- Type B1 devices showed a partially lifted zero-energy Landau level, revealing an insulating ν=0 quantum-Hall state.
- Type B2 devices exhibited full Landau level lifting and a gapped differential conductance even at zero magnetic field, indicating a spontaneously broken symmetry state with finite minimum conductance.
Conclusions:
- Bilayer graphene can host distinct insulating states, including quantum-Hall and spontaneously broken symmetry states.
- The spontaneously broken symmetry state in B2 devices is characterized by insulating bulk and compressible edge states.
- These findings highlight the rich electronic properties and potential for novel quantum phenomena in bilayer graphene.
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