1,094 research outputs found
Quantum-mechanical wavepacket transport in quantum cascade laser structures
We present a viewpoint of the transport process in quantum cascade laser
structures in which spatial transport of charge through the structure is a
property of coherent quantum-mechanical wavefunctions. In contrast, scattering
processes redistribute particles in energy and momentum but do not directly
cause spatial motion of charge.Comment: 6 pages, 5 figures included in tex, to appear in Physical Review
Optical phonon scattering and theory of magneto-polarons in a quantum cascade laser in a strong magnetic field
We report a theoretical study of the carrier relaxation in a quantum cascade
laser (QCL) subjected to a strong magnetic field. Both the alloy (GaInAs)
disorder effects and the Frohlich interaction are taken into account when the
electron energy differences are tuned to the longitudinal optical (LO) phonon
energy. In the weak electron-phonon coupling regime, a Fermi's golden rule
computation of LO phonon scattering rates shows a very fast non-radiative
relaxation channel for the alloy broadened Landau levels (LL's). In the strong
electron-phonon coupling regime, we use a magneto-polaron formalism and compute
the electron survival probabilities in the upper LL's with including increasing
numbers of LO phonon modes for a large number of alloy disorder configurations.
Our results predict a nonexponential decay of the upper level population once
electrons are injected in this state.Comment: 10 pages, 23 figure
Nanohelices as superlattices: Bloch oscillations and electric dipole transitions
Subjecting a nanohelix to a transverse electric field gives rise to superlattice behavior with tunable electronic properties. We theoretically investigate such a system and find Bloch oscillations and negative differential conductance when a longitudinal electric field (along the nanohelix axis) is also applied. Furthermore, we study dipole transitions across the transverse-electric-field-induced energy gap, which can be tuned to the eulogized terahertz frequency range by experimentally attainable external fields. We also reveal a photogalvanic effect by shining circularly polarized light onto our helical quantum wire.We acknowledge financial support from the CNRS and from the ANR under Grant No. ANR-14-CE26-0005 Q-MetaMat, as well as the EU H2020 RISE project CoExAN (Grant No. H2020-644076), EU FP7 ITN NOTEDEV (Grant No. FP7-607521), and the FP7 IRSES projects CANTOR (Grant No. FP7-612285), QOCaN (Grant No. FP7-316432), and InterNoM (Grant No. FP7-612624)
Large Rapidity Gap Processes in Proton-Nucleus Collisions
The cross sections for a variety of channels of proton-nucleus interaction
associated with large gaps in rapidity are calculated within the Glauber-Gribov
theory. We found inelastic shadowing corrections to be dramatically enhanced
for such events. We employ the light-cone dipole formalism which allows to
calculate the inelastic corrections to all orders of the multiple interaction.
Although Gribov corrections are known to make nuclear matter more transparent,
we demonstrate that in some instances they lead to an opaqueness. Numerical
calculations are performed for the energies of the HERA-B experiment, and the
RHIC-LHC colliders.Comment: 19 page
Diffractive gauge bosons production beyond QCD factorisation
We discuss single diffractive gauge bosons ()
production in proton-proton collisions at different (LHC and RHIC) energies
within the color dipole approach. The calculations are performed for gauge
bosons produced at forward rapidities. The diffractive cross section is
predicted as function of fractional momentum and invariant mass of the lepton
pair. We found a dramatic breakdown of the diffractive QCD factorisation caused
by an interplay of hard and soft interactions. Data from the CDF experiment on
diffractive production of and are well explained in a parameter free
way.Comment: 28 pages, 10 figures; a clarification of absorptive corrections has
been added, typos corrected; the published versio
Geophysical characteristics and structural composition of clay rocks in the terrigenous complex of the southeastern part of the West Siberian oil and gas bearing pro
The basic attributes identifying the clay rock composition in the terrigenous complex of the southeastern part of the West-Siberian platform have been determined, based on the correlation of structural composition and geophysical data, including induced potential logging, apparent resistivity, induction logging, radioactive and caliper logging. According to the obtained results it is possible to identify above-mentioned rocks in well logs, even under conditions of limited core samples, their application in well log correlation and back stripping. Key words: geophysical well logging, the West-Siberian oil and gas bearing province, terrigenous complex, clay rocks, back stripping
Subband population in a single-wall carbon nanotube diode
We observe current rectification in a molecular diode consisting of a
semiconducting single-wall carbon nanotube and an impurity. One half of the
nanotube has no impurity, and it has a current-voltage (I-V) charcteristic of a
typical semiconducting nanotube. The other half of the nanotube has the
impurity on it, and its I-V characteristic is that of a diode. Current in the
nanotube diode is carried by holes transported through the molecule's
one-dimensional subbands. At 77 Kelvin we observe a step-wise increase in the
current through the diode as a function of gate voltage, showing that we can
control the number of occupied one-dimensional subbands through electrostatic
doping.Comment: to appear in Physical Review Letters. 4 pages & 3 figure
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