317 research outputs found
Polarization dependence of emission spectra of multiexcitons in self-assembled quantum dots
We have investigated the polarization dependence of the emission spectra of
p-shell multiexcitons of a quantum dot when the single particle level spacing
is larger than the characteristic energy of the Coulomb interactions. We find
that there are many degenerate multiexciton states. The emission intensities
depend on the number of degenerate initial and final states of the optical
transitions. However, unlike the transition energies, they are essentially
independent of the strength of the Coulomb interactions. In the presence of
electron-hole symmetry the independence is exact.Comment: 7 pages, 5 figures, published in Solid State Commu
Time-resolved spectroscopy of multi-excitonic decay in an InAs quantum dot
The multi-excitonic decay process in a single InAs quantum dot is studied
through high-resolution time-resolved spectroscopy. A cascaded emission
sequence involving three spectral lines is seen that is described well over a
wide range of pump powers by a simple model. The measured biexcitonic decay
rate is about 1.5 times the single-exciton decay rate. This ratio suggests the
presence of selection rules, as well as a significant effect of the Coulomb
interaction on the biexcitonic wavefunction.Comment: one typo fixe
Optimum Arrangement of Resonator in Micro-bunch Free Electron Laser(III. Accelerator, Synchrotron Radiation, and Instrumentation)
Using a short-bunched beam of electrons from a linear accelator, the output of the micro-bunch FEL has been studied experimentally to clarify the optimum arrangement of an open resonator on the electron orbit. The output depends sharply on the arrangement, and the maximum output is observed when the resonator axis intersects the electron orbit with the angle of 3°
Millisecond-range electron spin memory in singly-charged InP quantum dots
We report millisecond-range spin memory of resident electrons in an ensemble
of InP quantum dots (QDs) under a small magnetic field of 0.1 T applied along
the optical excitation axis at temperatures up to about 5 K. A pump-probe
photoluminescence (PL) technique is used for optical orientation of electron
spins by the pump pulses and for study of spin relaxation over the long time
scale by measuring the degree of circular polarization of the probe PL as a
function of pump-probe delay. Dependence of spin decay rate on magnetic field
and temperature suggests two-phonon processes as the dominant spin relaxation
mechanism in this QDs at low temperatures.Comment: 3 pages, 4 figures, submitted to Appl. Phys. Let
The phase-separated states in antiferromagnetic semiconductors with polarizable lattice
The possibility of the slab or stripe phase separation (alternating
ferromagnetic highly- conductive and insulating antiferromagnetic layers) is
proved for isotropic degenerate antiferromagnetic semiconductors. This type of
phase separation competes with the droplet phase separation (ferromagnetic
droplets in the antiferromagnetic host or vice versa). The interaction of
electrons with optical phonons alone cannot cause phase-separated state with
alternating highly-conductive and insulating regions but it stabilizes the
magnetic phase separation. The magnetostriction deformation of the lattice in
the phase-separated state is investigated.Comment: 17 Pages, 1 EPS Figur
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