5,989 research outputs found
Nonequilibrium nuclear-electron spin dynamics in semiconductor quantum dots
We study the spin dynamics in charged quantum dots in the situation where the
resident electron is coupled to only about 200 nuclear spins and where the
electron spin splitting induced by the Overhauser field does not exceed
markedly the spectral broadening. The formation of a dynamical nuclear
polarization as well as its subsequent decay by the dipole-dipole interaction
is directly resolved in time. Because not limited by intrinsic nonlinearities,
almost complete nuclear polarization is achieved, even at elevated
temperatures. The data suggest a nonequilibrium mode of nuclear polarization,
distinctly different from the spin temperature concept exploited on bulk
semiconductorsComment: 5 pages, 4 figure
Sub-nanosecond delay of light in (Cd,Zn)Te crystal
We study excitonic polariton relaxation and propagation in bulk CdZnTe using
time- resolved photoluminescence and time-of-flight techniques. Propagation of
picosecond optical pulses through 0.745 mm thick crystal results in time delays
up to 350 ps, depending on the photon energy. Optical pulses with 150 fs
duration become strongly stretched. The spectral dependence of group velocity
is consistent with the dispersion of the lower excitonic polariton branch. The
lifetimes of excitonic polariton in the upper and lower branches are 1.5 and 3
ns, respectively.Comment: 5 pages, 4 figure
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