412 research outputs found
Kinetics of the inner ring in the exciton emission pattern in GaAs coupled quantum wells
We report on the kinetics of the inner ring in the exciton emission pattern.
The formation time of the inner ring following the onset of the laser
excitation is found to be about 30 ns. The inner ring was also found to
disappear within 4 ns after the laser termination. The latter process is
accompanied by a jump in the photoluminescence (PL) intensity. The spatial
dependence of the PL-jump indicates that the excitons outside of the region of
laser excitation, including the inner ring region, are efficiently cooled to
the lattice temperature even during the laser excitation. The ring formation
and disappearance are explained in terms of exciton transport and cooling.Comment: 19 pages, 6 figure
Can the Benjamin-Feir instability spawn a rogue wave?
Abstract. Recent work by our research group has shown that wave damping can have a surprisingly strong effect on the evolution of waves in deep water, even when the damping is weak. Whether damping is or is not included in a theoretical model can change the outcome in terms of both stability of wave patterns and frequency downshifting. It is conceivable that it might affect the early development of rogue waves as well
Pancharatnam-Berry phase in condensate of indirect excitons
We report on the observation of the Pancharatnam-Berry phase in a condensate
of indirect excitons (IXs) in a GaAs coupled quantum well structure. The
Pancharatnam-Berry phase leads to phase shifts of interference fringes in IX
interference patterns. Correlations are found between the phase shifts,
polarization pattern of IX emission, and onset of IX spontaneous coherence. The
Pancharatnam-Berry phase is acquired due to coherent spin precession in IX
condensate. The effect of the Pancharatnam-Berry phase on the IX phase pattern
is described in terms of an associated momentum.Comment: 6 pages, 5 figures + 2 pages supplemental material, 3 supplemental
figure
Instrument manual for the retarding ion mass spectrometer on Dynamics Explorer-1
The retarding ion mass spectrometer (RIMS) for Dynamics Explorer-1 is an instrument designed to measure the details of the thermal plasma distribution. It combines the ion temperature determining capability of the retarding potential analyzer with the compositional capabilities of the mass spectrometer and adds multiple sensor heads to sample all directions relative to the spacecraft ram direction. This manual provides a functional description of the RIMS, the instrument calibration, and a description of the commands which can be stored in the instrument logic to control its operation
Electrostatic Conveyer for Excitons
We report on the study of indirect excitons in moving lattices - conveyers
created by a set of AC voltages applied to the electrodes on the sample
surface. The wavelength of this moving lattice is set by the electrode
periodicity, the amplitude is controlled by the applied voltage, and the
velocity is controlled by the AC frequency. We observed the dynamical
localization-delocalization transition for excitons in the conveyers and
measured its dependence on the exciton density and conveyer amplitude and
velocity. We considered a model for exciton transport via conveyers. The
theoretical simulations are in agreement with the experimental data.Comment: 4 pages, 4 figures + supplemental material including two video
Spin Texture in a Cold Exciton Gas
We report on the observation of a spin texture in a cold exciton gas in a
GaAs/AlGaAs coupled quantum well structure. The spin texture is observed around
the exciton rings. The observed phenomena include: a ring of linear
polarization, a vortex of linear polarization with polarization perpendicular
to the radial direction, an anisotropy in the exciton flux, a skew of the
exciton fluxes in orthogonal circular polarizations and a corresponding
four-leaf pattern of circular polarization, a periodic spin texture, and
extended exciton coherence in the region of the polarization vortex. The data
indicate a transport regime where the spin polarization is locked to the
direction of particle propagation and scattering is suppressed.Comment: version 2 contains updated supplementary materia
Effect of spatial resolution on the estimates of the coherence length of excitons in quantum wells
We evaluate the effect of diffraction-limited resolution of the optical
system on the estimates of the coherence length of 2D excitons deduced from the
interferometric study of the exciton emission. The results are applied for
refining our earlier estimates of the coherence length of a cold gas of
indirect excitons in coupled quantum wells [S. Yang et al., Phys. Rev. Lett.
97, 187402(2006)]. We show that the apparent coherence length is well
approximated by the quadratic sum of the actual exciton coherence length and
the diffraction correction given by the conventional Abbe limit divided by
3.14. In practice, accounting for diffraction is necessary only when the
coherence length is smaller than about one wavelength. The earlier conclusions
regarding the strong enhancement of the exciton coherence length at low
temperatures remain intact.Comment: 6 pages, 5 figure
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