2,503 research outputs found
Electric field sensing with a scanning fiber-coupled quantum dot
We demonstrate the application of a fiber-coupled quantum-dot-in-a-tip as a
probe for scanning electric field microscopy. We map the out-of-plane component
of the electric field induced by a pair of electrodes by measurement of the
quantum-confined Stark effect induced on a quantum dot spectral line. Our
results are in agreement with finite element simulations of the experiment.
Furthermore, we present results from analytic calculations and simulations
which are relevant to any electric field sensor embedded in a dielectric tip.
In particular, we highlight the impact of the tip geometry on both the
resolution and sensitivity.Comment: 10 pages, 4 figure
Effect of growth conditions on optical properties of CdSe/ZnSe single quantum dots
In this work, we have investigated the optical properties of two samples of
CdSe quantum dots by using submicro-photoluminescence spectroscopy. The effect
of vicinal-surface GaAs substrates on their properties has been also assessed.
The thinner sample, grown on a substrate with vicinal surface, includes only
dots with a diameter of less than 10 nm (type A islands). Islands of an average
diameter of about 16 nm (type B islands) that are related to a phase transition
via a Stranski-Krastanow growth process are also distributed in the thicker
sample grown on an oriented substrate. We have studied the evolution of
lineshapes of PL spectra for these two samples by improving spatial resolution
that was achieved using nanoapertures or mesa structures. It was found that the
use of a substrate with the vicinal surface leads to the suppression of
excitonic PL emitted from a wetting layer.Comment: 2pages, 2 figures, Proceedings of International Conference On
Superlattices Nano-Structures And Nano-Devices, July, Toulouse, France, to
appear in the special issue of Physica
B-> rho pi, rho rho, pi pi: hunting for alpha
We determine the domains of the values of unitarity triangle angle alpha,
allowed by the charmless strangeless B_d (\bar B_d) decays.Comment: 16 pages. Recent Belle results on CP asymmetries in
B_d(\bar{B}_d)-->rho^+ rho^- decays are taken into account. Version to be
published in Yad.Fi
Thermal Quantum Fields without Cut-offs in 1+1 Space-time Dimensions
We construct interacting quantum fields in 1+1 dimensional Minkowski space,
representing neutral scalar bosons at positive temperature. Our work is based
on prior work by Klein and Landau and Hoegh-KrohnComment: 48 page
Infrared problem for the Nelson model on static space-times
We consider the Nelson model with variable coefficients and investigate the
problem of existence of a ground state and the removal of the ultraviolet
cutoff. Nelson models with variable coefficients arise when one replaces in the
usual Nelson model the flat Minkowski metric by a static metric, allowing also
the boson mass to depend on position. A physical example is obtained by
quantizing the Klein-Gordon equation on a static space-time coupled with a
non-relativistic particle. We investigate the existence of a ground state of
the Hamiltonian in the presence of the infrared problem, i.e. assuming that the
boson mass tends to 0 at infinity
Is the standard Higgs scalar elementary?
In the standard electroweak model, the measured top quark mass requires a
sizeable Yukawa coupling to the fundamental scalar. This large coupling alone
might induce a dynamical breaking of the electroweak symmetry as well as
non-perturbative effects. If such is the case, even a standard Higgs scalar as
light as 80 GeV should have a non-negligible component induced by
the top condensate.Comment: 8 pages, Latex fil
Correlated Photon Emission from a Single II-VI Quantum Dot
We report correlation and cross-correlation measurements of photons emitted
under continuous wave excitation by a single II-VI quantum dot (QD) grown by
molecular-beam epitaxy. A standard technique of microphotoluminescence combined
with an ultrafast photon correlation set-up allowed us to see an antibunching
effect on photons emitted by excitons recombining in a single CdTe/ZnTe QD, as
well as cross-correlation within the biexciton ()-exciton ()
radiative cascade from the same dot. Fast microchannel plate photomultipliers
and a time-correlated single photon module gave us an overall temporal
resolution of 140 ps better than the typical exciton lifetime in II-VI QDs of
about 250ps.Comment: 4 pages, 3 figures, to appear in Appl. Phys. Let
Weak Phase From Ratio of Rates
The ratio of partial decay rates for charged and neutral mesons to final states provides information on the weak phase when augmented with information on the CP-violating asymmetry
in the mode. The requirements for a useful determination of
are examined in the light of present information about the decays , , and the corresponding charge-conjugate
modes. The effects of electroweak penguins and rescattering corrections are
noted, and proposals are made for estimating and measuring their importance.Comment: 16 pages, latex, 3 figures, revised version sent to Phys. Rev.
Scattering below critical energy for the radial 4D Yang-Mills equation and for the 2D corotational wave map system
We describe the asymptotic behavior as time goes to infinity of solutions of
the 2 dimensional corotational wave map system and of solutions to the 4
dimensional, radially symmetric Yang-Mills equation, in the critical energy
space, with data of energy smaller than or equal to a harmonic map of minimal
energy. An alternative holds: either the data is the harmonic map and the
soltuion is constant in time, or the solution scatters in infinite time
Novos cerambycidae (coleoptera) da coleção Odette Morvan, Kaw, Guiana Francesa: III
Novas espécies da Guiana Francesa são descritas e figuradas: Trestonia bilineta sp. nov. (Onciderini); Ischnolea odettae sp. nov. (Desmiphorini); Oreodera mageia sp. nov. (Acanthoderini) e Icupima ampliata sp. nov. (Hemilophini). Faz-se um novo registro de Plocaederus fragosoi (Cerambycini) para a Guiana Francesa.New Cerambycidae (Coleoptera) of the Collection Odette Morvan, Kaw, French Guiana. New species described and figured of French Guiana: Oreodera mageia sp. nov. (Acanthoderini; Trestonia bilineata sp. nov. (Onciderini); Ischnolea odettae sp. nov. (Desmiphorini) and Icupima ampliata sp. nov. (Hemilophini). Plocaederus fragosoi (Cerambycini) is recorded for French Guiana
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