976 research outputs found
Elastic theory of quantum Hall smectics: effects of disorder
We study the effect of disorder on quantum Hall smectics within the framework
of an elastic theory. Based on a renormalization group calculation, we derive
detailed results for the degrees of translational and orientational order of
the stripe pattern at zero temperature and carefully map out the disorder and
length-scale regimes in which the system effectively exhibits smectic, nematic,
or isotropic behavior. We show that disorder always leads to a finite density
of free dislocations and estimate the scale on which they begin to appear.Comment: 4 pages latex with 1 EPS figur
PRIVATE PARTICIPATION IN AGRICULTURAL EXTENSION IN NIGERIA AND BENIN: DETERMINING THE WILLINGNESS TO PAY FOR INFORMATION
A typical private good is defined by its excludability and rivalry characteristics. Information might not generate rivalry among its users. By contrast, excludability is certainly a characteristic of information and its delivery can generate incentives for private participation. This study examines farmers' preferences for seed of new rice varieties and their willingness to pay for related information in villages of Nigeria and Benin. Conjoint analysis is used to estimate the structure of farmers' preferences for rice seed given a set of alternatives. Farmers are considered to be maximizers of utility rather than profit, preferring one variety over another based on the utility they obtain from its attributes, which depends on their own social and economic characteristics. Contingent methods are used to elicit preferences and willingness to pay (WTP) for rice seed. The marginal values of attributes, with and without information about the seed, are estimated with an ordered probit regression. WTP for information is derived from the analysis of WTP for rice seed. The results have implications for the best way to finance research and extension services in the areas of intervention, particularly for new rice varieties.WTP for information, conjoint analysis, rice attributes, farmers' preferences, Teaching/Communication/Extension/Profession, O3, O33, C35,
Discrete charging of a quantum dot strongly coupled to external leads
We examine a quantum dot with levels which is strongly coupled
to leads for varying number of channels in the leads. It is shown both
analytically and numerically that for strong couplings between the dot and the
leads, at least bound states (akin to subradiant states in
optics) remain on the dot. These bound states exhibit discrete charging and,
for a significant range of charging energies, strong Coulomb blockade behavior
as function of the chemical potential. The physics changes for large charging
energy where the same (superradiant) state is repeatedly charged.Comment: 5 pages, 3 figures (accepted for publication in EPL
Inelastic electron backscattering in a generic helical edge channel
We evaluate the low-temperature conductance of a weakly interacting
one-dimensional helical liquid without axial spin symmetry. The lack of that
symmetry allows for inelastic backscattering of a single electron, accompanied
by forward-scattering of another. This joint effect of weak interactions and
potential scattering off impurities results in a temperature-dependent
deviation from the quantized conductance, . In addition,
is sensitive to the position of the Fermi level. We determine
numerically the parameters entering our generic model for the
Bernevig-Hughes-Zhang Hamiltonian of a HgTe/CdTe quantum well in the presence
of Rashba spin-orbit coupling.Comment: 4+ pages, 3 figures, published versio
Localization Properties of Two Interacting Electrons in a Disordered Quasi One-Dimensional Potential
We study the transport properties of two electrons in a quasi one-dimensional
disordered wire. The electrons are subject to both, a disorder potential and a
short range two-body interaction. Using the approach developed by Iida et al. [
Ann. Phys. (N.Y.) 200 (1990) 219 ], the supersymmetry technique, and a suitable
truncation of Hilbert space, we work out the two-point correlation function in
the framework of a non-linear sigma model. We study the loop corrections to
arbitrary order. We obtain a remarkably simple and physically transparent
expression for the change of the localization length caused by the two-body
interaction.Comment: 10 page
Level Statistics and Localization for Two Interacting Particles in a Random Potential
We consider two particles with a local interaction in a random potential
at a scale (the one particle localization length). A simplified
description is provided by a Gaussian matrix ensemble with a preferential
basis. We define the symmetry breaking parameter
associated to the statistical invariance under change of basis. We show that
the Wigner-Dyson rigidity of the energy levels is maintained up to an energy
. We find that when (the
inverse lifetime of the states of the preferential basis) is smaller than
(the level spacing), and when . This implies that the two-particle localization length first
increases as before eventually behaving as .Comment: 4 pages REVTEX, 4 Figures EPS, UUENCODE
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