948 research outputs found
Screening in gated bilayer graphene via variational calculus
We analyze the response of bilayer graphene to an external transverse
electric field using a variational method. A previous attempt to do so in a
recent paper by Falkovsky [Phys. Rev. B 80, 113413 (2009)] is shown to be
flawed. Our calculation reaffirms the original results obtained by one of us
[E. McCann, Phys. Rev. B 74, 161403(R) (2006)] by a different method. Finally,
we generalize these original results to describe a dual-gated bilayer graphene
device.Comment: 4 pages, 1 figur
The Absence of the Fractional Quantum Hall Effect at High Landau Levels
We compare the energies of the Laughlin liquid and a charge density wave in a
weak magnetic field for the upper Landau level filling factors
and . The charge density wave period has been optimized and was found to
be , where is the cyclotron radius. We conclude that the
optimal charge density wave is more energetically preferable than the Laughlin
liquid for the Landau level numbers at and for at . This implies that the fractional quantum Hall effect
cannot be observed for , in agreement with the experiment.Comment: 12 pages, revtex, 2 PostScript figures are applied. Revised and
corrected version. Also available at http://www.mnhep.umn.edu/~mfogler
Cyclotron resonance in a two-dimensional electron gas with long-range randomness
We show that the the cyclotron resonance in a two-dimensional electron gas
has non-trivial properties if the correlation length of the disorder is larger
than the de Broglie wavelength: (a) the lineshape assumes three different forms
in strong, intermediate, and weak magnetic fields (b) at the transition from
the intermediate to the weak fields the linewidth suddenly collapses due to an
explosive growth in the fraction of electrons with a diffusive-type dynamics.Comment: A few typos correcte
Comment on ``Analytic Structure of One-Dimensional Localization Theory: Re-Examining Mott's Law''
The low-frequency conductivity of a disordered Fermi gas in one spatial
dimension is governed by the Mott-Berezinskii law . In a recent Letter [Phys. Rev. Lett. 84, 1760 (2000)]
A. O. Gogolin claimed that this law is invalid, challenging our basic
understanding of disordered systems and a massive amount of previous
theoretical work. We point out two calculational errors in Gogolin's paper.
Once we correct them, the Mott-Berezinskii formula is fully recovered. We also
present numerical results supporting the Mott-Berezinskii formula but ruling
out that of Gogolin.Comment: 1 page, 1 figure, RevTeX
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