104 research outputs found
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
Neutrality point of graphene with coplanar charged impurities
The ground-state and the transport properties of graphene subject to the
potential of in-plane charged impurities are studied. The screening of the
impurity potential is shown to be nonlinear, producing a fractal structure of
electron and hole puddles. Statistical properties of this density distribution
as well as the charge compressibility of the system are calculated in the
leading-log approximation. The conductivity depends logarithmically on
, the dimensionless strength of the Coulomb interaction. The theory is
asymptotically exact when is small, which is the case for graphene on
a substrate with a high dielectric constant.Comment: (v3) 4 pages main paper, 2 pages supplementary info, no figure
Electronic response of graphene to linelike charge perturbations
The problem of electrostatic screening of a charged line by undoped or weakly
doped graphene is treated beyond the linear-response theory. The induced
electron density is found to be approximately doping independent, n(x)~(log
x)^2/x^2, at intermediate distances x from the charged line. At larger x, twin
p-n junctions may form if the external perturbation is repulsive for graphene
charge carriers. The effect of such inhomogeneities on conductance and quantum
capacitance of graphene is calculated. The results are relevant for transport
properties of graphene grain boundaries and for local electrostatic control of
graphene with ultrathin gates.Comment: Fixed typos and added reference
Feshbach resonance of heavy exciton-polaritons
We study interactions between polaritons formed by hybridization of excitons
in a two-dimensional (2D) semiconductor with surface optical phonons or
plasmons. These quasiparticles have a high effective mass and can bind into
bipolaritons near a Feshbach-like scattering resonance. We analyze the phase
diagram of a many-body condensate of heavy polaritons and bipolaritons and
calculate their absorption and luminescence spectra, which can be measured
experimentally.Comment: 11 pages, 7 figure
Late Gas accretion onto Primordial Minihalos: a Model for Leo T, Dark Galaxies and Extragalactic High-Velocity Clouds
In this letter we revisit the idea of reionization feedback on dwarf galaxy
formation. We show that primordial minihalos with v_cir<20 km/s stop accreting
gas after reionization, as it is usually assumed, but in virtue of their
increasing concentration and the decreasing temperature of the intergalactic
medium as redshift decreases below z=3, they have a late phase of gas accretion
and possibly star formation. We expect that pre-reionization fossils that
evolved on the outskirts of the Milky Way or in isolation show a bimodal star
formation history with 12 Gyr old and <10 Gyr old population of stars. Leo T
fits with this scenario. Another prediction of the model is the possible
existence of a population of gas rich minihalos that never formed stars. More
work is needed to understand whether a subset of compact high-velocity clouds
can be identified as such objects or whether an undiscovered population exists
in the voids between galaxies.Comment: 5 pages, 4 figures, accepted version MNRAS 392, L4
Exchange interaction in quantum rings and wires in the Wigner-crystal limit
We present a controlled method for computing the exchange coupling in
correlated one-dimensional electron systems based on the relation between the
exchange constant and the pair-correlation function of spinless electrons. This
relation is valid in several independent asymptotic regimes, including low
electron density case, under the general condition of a strong spin-charge
separation. Explicit formulas for the exchange constant are obtained for thin
quantum rings and wires with realistic Coulomb interactions by calculating the
pair-correlation function via a many-body instanton approach. A remarkably
smooth interpolation between high and low electron density results is shown to
be possible. These results are applicable to the case of one-dimensional wires
of intermediate width as well. Our method can be easily generalized to other
interaction laws, such as the inverse distance squared one of the
Calogero-Sutherland-Moser model. We demonstrate excellent agreement with the
known exact results for the latter model and show that they are relevant for a
realistic experimental setup in which the bare Coulomb interaction is screened
by an edge of a two-dimensional electron gas.Comment: 12 pages, 5 figure
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