1,437 research outputs found
Ultrafast Coherent Spectroscopy of the Fermi Edge Singularity
In this work we present a theoretical description of the transient response
of the Fermi Edge Singularity (FES). We study the linear and the nonlinear
response of an n-doped QW to laser pulses in the Coherent Control (CC) and Four
Wave Mixing (FWM) Configurations. By means of a bosonization formalism we
calculate the FWM signal emitted by the sample when it is excited by pulses
spectrally peaked around the FES and we show that the long time behavior of the
nonlinear signal is very similar to the linear case.Comment: Conference paper (13 EP2DS
Fermionic Atoms in Optical Superlattices
Fermionic atoms in an optical superlattice can realize a very peculiar
Anderson lattice model in which impurities interact with each other through a
discretized set of delocalized levels. We investigate the interplay between
Kondo effect and magnetism under these finite-size features. We find that Kondo
effect can dominate over magnetism depending on the parity of the number of
particles per discretized set. We show how Kondo-induced resonances of
measurable size can be observed through the atomic interference pattern
Exciton Beats in GaAs Quantum Wells: Bosonic Representation and Collective Effects
We discuss light-heavy hole beats observed in transient optical experiments
in GaAs quantum wells in terms of a free-boson coherent state model. This
approach is compared with descriptions based on few-level representations.
Results lead to an interpretation of the beats as due to classical
electromagnetic interference. The boson picture correctly describes photon
excitation of extended states and accounts for experiments involving coherent
control of the exciton density and Rayleigh scattering beating.Comment: 4 pages, no figures. Accepted for publication in Solid State
Communication
Spontaneous patterns in coherently driven polariton microcavities
We consider a polariton microcavity resonantly driven by two external lasers
which simultaneously pump both lower and upper polariton branches at normal
incidence. In this setup, we study the occurrence of instabilities of the
pump-only solutions towards the spontaneous formation of patterns. Their
appearance is a consequence of the spontaneous symmetry breaking of
translational and rotational invariance due to interaction induced parametric
scattering. We observe the evolution between diverse patterns which can be
classified as single-pump, where parametric scattering occurs at the same
energy as one of the pumps, and as two-pump, where scattering occurs at a
different energy. For two-pump instabilities, stripe and chequerboard patterns
become the dominant steady-state solutions because cubic parametric scattering
processes are forbidden. This contrasts with the single-pump case, where
hexagonal patterns are the most common arrangements. We study the possibility
of controlling the evolution between different patterns. Our results are
obtained within a linear stability analysis and are confirmed by finite size
full numerical calculations.Comment: 15 pages, 9 figure
Quantitative Description of Strong-Coupling of Quantum Dots in Microcavities
We have recently developed a self-consistent theory of Strong-Coupling in the
presence of an incoherent pumping [arXiv:0807.3194] and shown how it could
reproduce quantitatively the experimental data [PRL 101, 083601 (2008)]. Here,
we summarize our main results, provide the detailed analysis of the fitting of
the experiment and discuss how the field should now evolve beyond merely
qualitative expectations, that could well be erroneous even when they seem to
be firmly established.Comment: Submitted to the AIP Conference Proceedings Series for the ICPS 2008
(Rio de Janeiro). 2 pages, reduced-quality figur
The electro production of d* dibaryon
dibaryon study is a critical test of hadron interaction models. The
electro production cross sections of have been calculated based on
the meson exchange current model and the cross section around 30 degree of 1
GeV electron in the laboratory frame is about 10 nb. The implication of this
result for the dibaryon search has been discussed.Comment: 12 pages, 12 figures, Late
Restrictions on the coherence of the ultrafast optical emission from an electron-hole pairs condensate
We report on the transfer of coherence from a quantum-well electron-hole
condensate to the light it emits. As a function of density, the coherence of
the electron-hole pair system evolves from being full for the low density
Bose-Einstein condensate to a chaotic behavior for a high density BCS-like
state. This degree of coherence is transfered to the light emitted in a damped
oscillatory way in the ultrafast regime. Additionally, the photon field
exhibits squeezing properties during the transfer time. We analyze the effect
of light frequency and separation between electron and hole layers on the
optical coherence. Our results suggest new type of ultrafast experiments for
detecting electron-hole pair condensation.Comment: 4 pages,3 figures, to be published in Physical Review Letters. Minor
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