2,393 research outputs found
Coulomb scattering with remote continuum states in quantum dot devices
Electron capture and emission by Coulomb scattering in self-assembled quantum
dot (QD) devices is studied theoretically. While the dependence of the Coulomb
scattering (Auger) rates on the local wetting layer electron density has been a
topic of intense research, we put special interest on the remote scattering
between QD electrons and continuum electrons originating from a quantum well,
doped bulk layers or metal contacts. Numerical effort is made to include all
microscopic transitions between the Fermi distributed continuum states. The
remote Coulomb scattering is investigated as a function of the electron
density, the distance from the QDs and the temperature. Our results are
compared with experimental observations, considering lifetime limitations in QD
memory structures as well as the electron emission in pn-diodes
Disentangling Dark Matter Dynamics with Directional Detection
Inelastic dark matter reconciles the DAMA anomaly with other null direct
detection experiments and points to a non-minimal structure in the dark matter
sector. In addition to the dominant inelastic interaction, dark matter
scattering may have a subdominant elastic component. If these elastic
interactions are suppressed at low momentum transfer, they will have similar
nuclear recoil spectra to inelastic scattering events. While upcoming direct
detection experiments will see strong signals from such models, they may not be
able to unambiguously determine the presence of the subdominant elastic
scattering from the recoil spectra alone. We show that directional detection
experiments can separate elastic and inelastic scattering events and discover
the underlying dynamics of dark matter models.Comment: 7 pages, 5 figures, references and figures update
Theory of Transmission through disordered superlattices
We derive a theory for transmission through disordered finite superlattices
in which the interface roughness scattering is treated by disorder averaging.
This procedure permits efficient calculation of the transmission thr ough
samples with large cross-sections. These calculations can be performed
utilizing either the Keldysh or the Landauer-B\"uttiker transmission
formalisms, both of which yield identical equations. For energies close to the
lowest miniband, we demonstrate the accuracy of the computationally efficient
Wannier-function approximation. Our calculations indicate that the transmission
is strongly affected by interface roughness and that information about scale
and size of the imperfections can be obtained from transmission data.Comment: 12 pages, 6 Figures included into the text. Final version with minor
changes. Accepted by Physical Review
The Dark Matter at the End of the Galaxy
Dark matter density profiles based upon Lambda-CDM cosmology motivate an
ansatz velocity distribution function with fewer high velocity particles than
the Maxwell-Boltzmann distribution or proposed variants. The high velocity tail
of the distribution is determined by the outer slope of the dark matter halo,
the large radius behavior of the Galactic dark matter density. N-body
simulations of Galactic halos reproduce the high velocity behavior of this
ansatz. Predictions for direct detection rates are dramatically affected for
models where the threshold scattering velocity is within 30% of the escape
velocity.Comment: 10 pages, 5 figure
Spectrum of Curvature Perturbation of Multi-field Inflation with Small-Field Potential
In this paper, we have studied the spectrum of curvature perturbation of
multi-field inflation with general small-field potential. We assume that the
isocurvature perturbation may be neglected, and by using the Sasaki-Stewart
formalism, we found that the spectrum may be redder or bluer than of its
corresponding single field. The result depends upon the values of fields and
their effective masses at the horizon-crossing time. We discuss the relevant
cases.Comment: 8 pages, no figure, to publish in JCA
Effects of impurity scattering on electron-phonon resonances in semiconductor superlattice high-field transport
A non-equilibrium Green's function method is applied to model high-field
quantum transport and electron-phonon resonances in semiconductor
superlattices. The field-dependent density of states for elastic (impurity)
scattering is found non-perturbatively in an approach which can be applied to
both high and low electric fields. I-V curves, and specifically electron-phonon
resonances, are calculated by treating the inelastic (LO phonon) scattering
perturbatively. Calculations show how strong impurity scattering suppresses the
electron-phonon resonance peaks in I-V curves, and their detailed sensitivity
to the size, strength and concentration of impurities.Comment: 7 figures, 1 tabl
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