3,345 research outputs found
Comparisons of spectra determined using detector atoms and spatial correlation functions
We show how two level atoms can be used to determine the local time dependent
spectrum. The method is applied to a one dimensional cavity. The spectrum
obtained is compared with the mode spectrum determined using spatially filtered
second order correlation functions. The spectra obtained using two level atoms
give identical results with the mode spectrum. One benefit of the method is
that only one time averages are needed. It is also more closely related to a
realistic measurement scheme than any other definition of a time dependent
spectrum.Comment: 8 pages, 8 figure
Metal-insulator transition at B=0 in an ultra-low density () two dimensional GaAs/AlGaAs hole gas
We have observed a metal-insulator transition in an ultra-low density two
dimensional hole gas formed in a high quality GaAs-AlGaAs heterostructure at
B=0. At the highest carrier density studied () the hole gas is strongly metallic, with an exceptional mobility of
. The low disorder and strength of the many-body
interactions in this sample are highlighted by the observation of re-entrant
metal insulator transitions in both the fractional () and integer
() quantum Hall regimes. On reducing the carrier density the
temperature and electric field dependence of the resistivity show that the
sample is still metallic at (), becoming
insulating at . Our results indicate that
electron-electron interactions are dominant at these low densities, pointing to
the many body origins of this metal-insulator transition. We note that the
value of at the transition () is large enough to allow
the formation of a weakly pinned Wigner crystal, and is approaching the value
calculated for the condensation of a pure Wigner crystal.Comment: 4 pages, latex, 4 postscript figures, submitted to EP2DS-12 on 21st
August 1997, to appear in Physica
Phase separation and vortex states in binary mixture of Bose-Einstein condensates in the trapping potentials with displaced centers
The system of two simultaneously trapped codensates consisting of
atoms in two different hyperfine states is investigated theoretically in the
case when the minima of the trapping potentials are displaced with respect to
each other. It is shown that the small shift of the minima of the trapping
potentials leads to the considerable displacement of the centers of mass of the
condensates, in agreement with the experiment. It is also shown that the
critical angular velocities of the vortex states of the system drastically
depend on the shift and the relative number of particles in the condensates,
and there is a possibility to exchange the vortex states between condensates by
shifting the centers of the trapping potentials.Comment: 4 pages, 2 figure
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