# Anomalous exciton condensation in graphene bilayers.

@article{Barlas2010AnomalousEC,
title={Anomalous exciton condensation in graphene bilayers.},
author={Yafis Barlas and Ren{\'e} C{\^o}t{\'e} and Jules Lambert and Allan H. MacDonald},
journal={Physical review letters},
year={2010},
volume={104 9},
pages={
096802
}
}
In ordinary semiconductor bilayers, exciton condensates appear at total Landau-level filling factor nu{T}=1. We predict that similar states will occur in Bernal stacked graphene bilayers at many nonzero integer filling factors. For nu{T}=-3, 1 we find that the superfluid density of the exciton condensate vanishes and that a finite-temperature fluctuation-induced first order isotropic-smectic phase transition occurs when the layer densities are not balanced. These anomalous properties of bilayer… Expand
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#### References

SHOWING 1-10 OF 31 REFERENCES
Intra-Landau-level cyclotron resonance in bilayer graphene.
• Physics, Medicine
• Physical review letters
• 2008
It is predicted that an intra-Landau-level cyclotron resonance signal will appear at some odd-integer filling factors, accompanied by collective modes which are nearly gapless and have approximate k3/2 dispersion, and speculated on the possibility of unusual localization physics associated with these modes. Expand
Symmetry breaking in the zero-energy Landau level in bilayer graphene.
• Physics, Medicine
• Physical review letters
• 2010
Measurements of the activation energy gaps for the nu=2 and 3 filling factors in tilted magnetic fields exhibit no appreciable dependence on the in-plane magnetic field, suggesting that these Landau level splittings are independent of spin. Expand
Landau-level degeneracy and quantum Hall effect in a graphite bilayer.
• Physics, Medicine
• Physical review letters
• 2006
We derive an effective two-dimensional Hamiltonian to describe the low-energy electronic excitations of a graphite bilayer, which correspond to chiral quasiparticles with a parabolic dispersionExpand
Bias-voltage-induced phase transition in bilayer quantum Hall ferromagnets
• Physics
• 2002
We consider bilayer quantum Hall systems at total filling factor ν = 1 in presence of a bias voltage Δ ν that leads to different filling factors in each layer. We use auxiliary fieldExpand
Activated transport in the separate layers that form the nuT=1 exciton condensate.
The total filling factor nuT=1 quantum Hall state in a bilayer two-dimensional electron system with virtually no tunneling is observed and the activation energies show a striking asymmetry around the balance point. Expand
Bose–Einstein condensation of excitons in bilayer electron systems
• Physics, Medicine
• Nature
• 2004
Recent studies of semiconductor bilayer systems that provide clear evidence for exciton condensation in the quantum Hall regime are reviewed and why this phenomenon is as likely to occur in electron–electron bilayers as in electron-hole bilayers is explained. Expand
Intrinsic Zeeman Effect in Graphene
The intrinsic Zeeman energy is precisely one half of the cyclotron energy for electrons in graphene. As a result a Landau-level mixing occurs to create the energy spectrum comprised of the 4 j -foldExpand
Broken-Symmetry States and Divergent Resistance in Suspended Bilayer Graphene
• Physics, Materials Science
• 2009
D 0 state, the devices show extremely high magnetoresistance that scales as magnetic field divided by temperature. This resistance is predominantly affected by the perpendicular component of theExpand
Unconventional quantum Hall effect and Berry’s phase of 2π in bilayer graphene
There are two known distinct types of the integer quantum Hall effect. One is the conventional quantum Hall effect, characteristic of two-dimensional semiconductor systems1,2, and the other is itsExpand
Critical currents of ideal quantum Hall superfluids
• Physics
• 2003
Filling factor v=1 bilayer electron systems in the quantum Hall regime have an excitonic-condensate superfluid ground state when the layer separation d is less than a critical value d c . On aExpand