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Fabrication of Gate-tunable Graphene Devices for Scanning Tunneling Microscopy Studies with Coulomb Impurities
Published on: July 24, 2015
Dynamical screening and excitonic instability in bilayer graphene.
Rahul Nandkishore1, Leonid Levitov
1Department of Physics, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA.
Physical Review Letters
|May 21, 2010
Summary
Electron interactions cause instability in bilayer graphene, breaking symmetry and opening an energy gap. This excitonic instability is observable and scales with interaction strength.
Area of Science:
- Condensed Matter Physics
- Materials Science
- Quantum Mechanics
Background:
- Undoped bilayer graphene is typically a gapless semiconductor.
- Electron-electron interactions are crucial in low-dimensional materials.
- Understanding symmetry breaking is key to novel electronic properties.
Purpose of the Study:
- To investigate the instability of the gapless state in bilayer graphene.
- To theoretically model the effects of electron interactions on bilayer graphene.
- To understand the mechanism of energy gap opening at the Dirac point.
Main Methods:
- Development of a controlled theory for electron interactions.
- Inclusion of dynamically screened Coulomb interactions.
- Accounting for a dynamically generated ultraviolet cutoff.
Main Results:
- Electron interactions induce an instability in the gapless state of bilayer graphene.
- "Which-layer" symmetry breaking and energy gap opening occur at the Dirac point.
- The energy gap exhibits a power-law scaling with interaction strength.
Conclusions:
- Bilayer graphene is unstable to electron interactions, unlike single-layer graphene.
- The excitonic instability is observable and theoretically described.
- This phenomenon offers a route to engineer electronic properties in graphene.
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