# 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

#### Figures and Topics from this paper

#### 26 Citations

Quantum Hall ferroelectric helix in bilayer graphene

- Physics
- Physical Review B
- 2019

We re-examine the nature of the ground states of bilayer graphene at odd integer filling factors within a simplified model of nearly degenerate $n=0$ and $n=1$ Landau levels. Previous Hartree-Fock… Expand

Symmetry Breaking in Graphene’s Quantum Hall Regime: The Competition Between Interactions and Disorder

- Physics
- 2014

Graphene is a two-dimensional carbon material with a honeycomb lattice and Dirac-like low-energy excitations. When Zeeman interaction is neglected its Landau levels are four-fold degenerate,… Expand

Excitonic condensation for the surface states of topological insulator bilayers

- Physics
- 2011

We propose a generic topological insulator bilayer (TIB) system to study the excitonic condensation with self-consistent mean-field (SCMF) theory. We show that the TIB system presents the crossover… Expand

Single-layer graphene with electronic properties of a gated bilayer

- Physics, Materials Science
- Physical Review B
- 2019

We demonstrate that single layer graphene exhibits the electronic structure of a bilayer when it is connected to two gated bilayers. The energy gap characteristic for gated bilayer is induced in the… Expand

Many-body effects, orbital mixing, and cyclotron resonance in bilayer graphene

- Physics
- 2020

In a magnetic field bilayer graphene supports, at the lowest Landau level, eight characteristic zero-energy levels with an extra twofold degeneracy in Landau orbitals $n=\{0,1\}$. They, under general… Expand

Interaction-enhanced electron-hole and valley asymmetries in the lowest Landau level ofABA-stacked trilayer graphene

- Physics
- 2014

In a magnetic field graphene trilayers support a special multiplet of 12 zero(-energy)-mode Landau levels with a threefold degeneracy in Landau orbitals. A close look is made into such zero-mode… Expand

Quantum Hall ferromagnetic phases in the Landau levelN=0of a graphene bilayer

- Physics
- 2013

In a Bernal-stacked graphene bilayer, an electronic state in Landau level $% N=0$ is described by its guiding-center index $X$ (in the Landau gauge) and by its valley, spin, and orbital indices $\xi… Expand

Existence of nontrivial topologically protected states at grain boundaries in bilayer graphene: signatures and electrical switching.

- Physics, Materials Science
- Nanoscale
- 2016

This work shows that the appearance of the topologically protected states in stacking domain walls can be much more common in bilayer graphene, since they can also emerge in unexpected geometries, e.g., at grain boundaries with atomic-scale topological defects. Expand

Phase diagram of insulating crystal and quantum Hall states in ABC-stacked trilayer graphene

- Physics
- 2012

In the presence of a perpendicular magnetic field, ABC-stacked trilayer graphene's chiral band structure supports a 12-fold degenerate N=0 Landau level (LL). Along with the valley and spin degrees of… Expand

Quantum Hall effects in graphene-based two-dimensional electron systems.

- Physics, Medicine
- Nanotechnology
- 2012

It is explained why graphene and bilayer graphene can be viewed respectively as J D 1 and 2 chiral two-dimensional electron gases (C2DEGs), and why this property frames their quantum Hall physics. Expand

#### 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 dispersion… Expand

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 field… Expand

Activated transport in the separate layers that form the nuT=1 exciton condensate.

- Materials Science, Medicine
- Physical review letters
- 2004

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

- Physics
- 2007

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 -fold… Expand

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 the… Expand

Unconventional quantum Hall effect and Berry’s phase of 2π in bilayer graphene

- Physics
- 2006

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 its… Expand

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 a… Expand