149,148 research outputs found
Phonon Coherence and New Set of Sidebands in Phonon-Assisted Photoluminescence
We investigate excitonic polaron states comprising a local exciton and
phonons in the longitudinal optical (LO) mode by solving the Schr\"{o}dinger
equation. We derive an exact expression for the ground state (GS), which
includes multi-phonon components with coefficients satisfying the Huang-Rhys
factors. The recombination of GS and excited polaron states gives one set of
sidebands in photoluminescence (PL): the multi-phonon components in the GS
produce the Stokes lines and the zero-phonon components in the excited states
produce the anti-Stokes lines. By introducing the mixing of the LO mode and
environal phonon modes, the exciton will also couple with the latter, and the
resultant polaron states result in another set of phonon sidebands. This set
has a zero-phonon line higher and wider than that of the first set due to the
tremendous number of the environal modes. The energy spacing between the
zero-phonon lines of the first and second sets is proved to be the binding
energy of the GS state. The common exciton origin of these two sets can be
further verified by a characteristic Fano lineshape induced by the coherence in
the mixing of the LO and the environal modes.Comment: 5 pages, 3 figures 1 figure (fig. 1) replaced 1 figure (fig. 2)
remove
Leggett-Garg inequalities for the statistics of electron transport
We derive a set of Leggett-Garg inequalities (temporal Bell's inequalities)
for the moment generating function of charge transferred through a conductor.
Violation of these inequalities demonstrates the absence of a macroscopic-real
description of the transport process. We show how these inequalities can be
violated by quantum-mechanical systems and consider transport through normal
and superconducting single-electron transistors as examples.Comment: 5 pages; 3 figure
Recommended from our members
Investigate the impacts of assimilating satellite rainfall estimates on rainstorm forecast over southwest United States
Using the MM5-4DVAR system, a monsoon rainstorm case over southern Arizona (5-6 August 2002) was investigated for the influence of assimilating satellite rainfall estimates on precipitation forecasts. A set of numerical experiments was conducted with multiple configurations including using 20-km or 30-km grid distances and none or 3-h or 6-h assimilation time windows. Results show that satellite rainfall assimilation can improve the rainstorm-forecasting pattern and amount to some extent. The minimization procedure of 4DVAR is sensitive to model spatial resolution and the assimilation time window. The 3-h assimilation window with hourly rainfall data works well for the 6-h forecast, and for 12-h or longer forecasts, a 6-h assimilation window will be requested. Copyright 2004 by the American Geophysical Union
A study of physical processes for space radiation protection
The determination of stopping power for monatomic molecules and water vapor is addressed. Intermediate and low energy protons are considered
Recommended from our members
Impact of assimilating rainfall derived from radar and satellites on rainstorm forecasts over the Southwestern United States
The impact of assimilating rainfall derived from radar and satellites on rainstorm forecasts over the Southwestern United States is discussed. The major advantage of 4DVAR is the use of full model dynamics and physics to assimilate multiple-time-level observation data. Rainfall assimilation via 4DVAR is used to improve the moisture distributions in model IC. It is found that by using 4DVAR to generate model IC, the precipitation intensity and patterns can be improved substantially over the mid-latitude plain regions
Narrow-line Seyfert 1 Galaxies and the M_BH - sigma Relation
We have studied the location of narrow-line Seyfert 1 (NLS1) galaxies and
broad-line Seyfert 1 (BLS1) galaxies on the M_BH - sigma relation of non-active
galaxies. We find that NLS1 galaxies as a class - as well as the BLS1 galaxies
of our comparison sample - do follow the M_BH-sigma relation of non-active
galaxies if we use the width of the [SII]6716,6731 emission lines as surrogate
for stellar velocity dispersion, sigma_*. We also find that the width of
[OIII]5007 is a good surrogate for sigma_*, but only after (a) removal of
asymmetric blue wings, and, more important, after (b) excluding core [OIII]
lines with strong blueshifts (i.e., excluding galaxies which have their [OIII]
velocity fields dominated by radial motions, presumably outflows). The same
galaxies which are extreme outliers in [OIII] still follow the M_BH - sigma
relation in [SII]. We confirm previous findings that NLS1 galaxies are
systematically off-set from the M_BH - sigma relation if the full [OIII]
profile is used to measure sigma. We systematically investigate the influence
of several parameters on the NSL1 galaxies' location on the M_BH - sigma plane:
[OIII]_core blueshift, L/L_Edd, intensity ratio FeII/H_beta, NLR density, and
absolute magnitude. Implications for NLS1 models and for their evolution along
the M_BH - sigma relation are discussed.Comment: ApJ Letters, in press (3 figures, one in colour
Magnetic field induced enhancement of spin-order peak intensity in La(1.875)Ba(0.125)CuO(4)
We report on neutron-scattering results on the impact of a magnetic field on
stripe order in the cuprate LaBaCuO. It is found that a
7 T magnetic field applied along the {\it c} axis causes a small but finite
enhancement of the spin-order peak intensity and has no observable effect on
the peak width. Inelastic neutron-scattering measurements indicate that the
low-energy magnetic excitations are not affected by the field, within
experimental error. In particular, the small energy gap that was recently
reported is still present at low temperature in the applied field. In addition,
we find that the spin-correlation length along the antiferromagnetic stripes is
greater than that perpendicular to them.Comment: 4 pages, 5 figure
- …