Anomalous exciton condensation in graphene bilayers.

  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},
  volume={104 9},
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… 

Figures from this paper

Quantum Hall ferroelectric helix in bilayer graphene

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

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

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,

Excitonic condensation for the surface states of topological insulator bilayers

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

Single-layer graphene with electronic properties of a gated bilayer

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

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

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

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

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.

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

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

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

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.

Electron–hole pair condensation and Coulomb drag effect in a graphene double layer

  • Chuanyi ZhangG. Jin
  • Physics
    Journal of physics. Condensed matter : an Institute of Physics journal
  • 2013
There exists a minimum drag conductivity by increasing the gate voltage, which results from the combined effect of the longitudinal conductivity in each graphene layer and superfluid density, which is especially useful for detecting the pair condensation experimentally.

Coherence and Optical Emission from Bilayer Exciton Condensates

Experiments aimed at demonstrating Bose-Einstein condensation of excitons in two types of experiments with bilayer structures (coupled quantum wells) are reviewed, with an emphasis on the basic



Intra-Landau-level cyclotron resonance in bilayer graphene.

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.

Symmetry breaking in the zero-energy Landau level in bilayer graphene.

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.

Landau-level degeneracy and quantum Hall effect in a graphite bilayer.

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

Bias-voltage-induced phase transition in bilayer quantum Hall ferromagnets

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

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.

Bose–Einstein condensation of excitons in bilayer electron systems

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.

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 -fold

Broken-Symmetry States and Divergent Resistance in Suspended Bilayer Graphene

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

Critical currents of ideal quantum Hall superfluids

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

Chirality and correlations in graphene.

Graphene's exchange and random-phase-approximation correlation energies are evaluated to show that the tendency of Coulomb interactions in lightly doped graphene to favor states with larger net chirality leads to suppressed spin and charge susceptibilities.