4,565 research outputs found
Rectification of displacement currents in an adiabatic electron pump
Rectification of ac displacement currents generated by periodic variation of
two independent gate voltages of a quantum dot can lead to a dc voltage linear
in the frequency. The presence of this rectified displacement current could
account for the magnetic field symmetry observed in a recent measurement on an
adiabatic quantum electron pump by Switkes et al. [Science 283, 1905 (1999)].Comment: 2 pages, RevTeX; 1 figur
Endstates in multichannel spinless p-wave superconducting wires
Multimode spinless p-wave superconducting wires with a width W much smaller
than the superconducting coherence length \xi are known to have multiple
low-energy subgap states localized near the wire's ends. Here we compare the
typical energies of such endstates for various terminations of the wire: A
superconducting wire coupled to a normal-metal stub, a weakly disordered
superconductor wire and a wire with smooth confinement. Depending on the
termination, we find that the energies of the subgap states can be higher or
lower than for the case of a rectangular wire with hard-wall boundaries.Comment: 10 pages, 7 figure
Intensity distribution of scalar waves propagating in random media
Transmission of the scalar field through the random medium, represented by
the system of randomly distributed dielectric cylinders is calculated
numerically. System is mapped to the problem of electronic transport in
disordered two-dimensional systems. Universality of the statistical
distribution of transmission parameters is analyzed in the metallic and in the
localized regimes.In the metallic regime the universality of the transmission
statistics in all transparent channels is observed. In the band gaps, we
distinguish the disorder induced (Anderson) localization from the tunneling
through the system due to the gap in the density of states. We show also that
absorption causes rapid decrease of the mean conductance, but, contrary to the
localized regime, the conductance is self-averaged with a
Gaussian distribution
Decay Rate Distributions of Disordered Slabs and Application to Random Lasers
We compute the distribution of the decay rates (also referred to as residues)
of the eigenstates of a disordered slab from a numerical model. From the
results of the numerical simulations, we are able to find simple analytical
formulae that describe those results well. This is possible for samples both in
the diffusive and in the localised regime. As example of a possible
application, we investigate the lasing threshold of random lasers.Comment: 11 pages, 11 figure
Decision uncertainty in multi-attribute stated preference studies
Econometric modelling of decision uncertainty has received extensive attention in the contingent valuation literature, but these methods are not directly transferable to the realm of multi-attribute stated preference studies. In this paper, an integrated choice and latent variable model tracing the impact of decision uncertainty on the valuation of flood risks reductions in the Netherlands is developed. The proposed model structure is not subject to the potential endogeneity bias and measurement error issues associated with most applied methods. The driving factors of decision uncertainty are identified through stated choices and a set of self-reported decision uncertainty follow-up questions. The model simultaneously accounts for the impact of decision uncertainty on individual choices and welfare estimates. In the presented case study, uncertain respondents are found to make more random choices and select the opt out option more often. Willingness-to-pay for flood risk reductions increases after accounting for these behavioural responses to decision uncertainty
Synthesis and Spectroscopic Characterization of 1,​8-​Naphthalimide Derived "Super" Photoacids
The ground- and excited-​state acid-​base properties of three novel naphthalimide-​based "super" photoacids were studied using steady-​state and time-​resolved spectroscopy. The compds. exhibit pKa = 8.8-​8.0 and pK*a = -​1.2 to -​1.9. The decrease in both ground- and excited-​state pKa is achieved by attachment of an electron withdrawing group (sulfonate) on the arom. system. All compds. are deprotonated upon excitation in alcs. and DMSO. Good correlation is established between the pK*a and the ratio of the neutral and anion emission intensities in a certain solvent. The excited-​state intermol. proton transfer to solvent (H2O and DMSO) is explained by a two-​step model. In the first step, short-​range proton transfer takes place, resulting in the formation of a contact ion pair. Free ion pairs are formed in the diffusion controlled second step
Quantum mechanical time-delay matrix in chaotic scattering
We calculate the probability distribution of the matrix Q = -i \hbar S^{-1}
dS/dE for a chaotic system with scattering matrix S at energy E. The
eigenvalues \tau_j of Q are the so-called proper delay times, introduced by E.
P. Wigner and F. T. Smith to describe the time-dependence of a scattering
process. The distribution of the inverse delay times turns out to be given by
the Laguerre ensemble from random-matrix theory.Comment: 4 pages, RevTeX; to appear in Phys. Rev. Let
Fokker-Planck equations and density of states in disordered quantum wires
We propose a general scheme to construct scaling equations for the density of
states in disordered quantum wires for all ten pure Cartan symmetry classes.
The anomalous behavior of the density of states near the Fermi level for the
three chiral and four Bogoliubov-de Gennes universality classes is analysed in
detail by means of a mapping to a scaling equation for the reflection from a
quantum wire in the presence of an imaginary potential.Comment: 10 pages, 5 figures, revised versio
Vortices on a superconducting nanoshell: phase diagram and dynamics
In superconductors, the search for special vortex states such as giant
vortices focuses on laterally confined or nanopatterned thin superconducting
films, disks, rings, or polygons. We examine the possibility to realize giant
vortex states and states with non-uniform vorticity on a superconducting
spherical nanoshell, due to the interplay of the topology and the applied
magnetic field. We derive the phase diagram and identify where, as a function
of the applied magnetic field, the shell thickness and the shell radius, these
different vortex phases occur. Moreover, the curved geometry allows these
states (or a vortex lattice) to coexist with a Meissner state, on the same
curved film. We have examined the dynamics of the decay of giant vortices or
states with non-uniform vorticity into a vortex lattice, when the magnetic
field is adapted so that a phase boundary is crossed.Comment: 21 pages, 9 figure
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