128,030 research outputs found
Spectral Line Width Broadening from Pair Fluctuation in a Frozen Rydberg Gas
Spectral line width broadening in Rydberg gases, a phenomenon previously
attributed to the many-body effect, was observed experimentally almost a decade
ago. The observed line width was typically 80-100 times larger than the average
interaction strength predicted from a binary interaction. The interpretation of
such a phenomenon is usually based on the so-called diffusion model, where the
line width broadening mostly originates from the diffusion of excitations. In
this paper, we present a model calculation to show that diffusion is not the
main mechanism to the line width broadening. We find that the rare pair
fluctuation at small separation is the dominant factor contributing to this
broadening. Our results give a width of about 20-30 times larger than the
average interaction strength. More importantly, by turning off the diffusion
process, we do not observe order of magnitude change in the spectral line
width
Unchanged thermopower enhancement at the semiconductor-metal transition in correlated FeSbTe
Substitution of Sb in FeSb by less than 0.5% of Te induces a transition
from a correlated semiconductor to an unconventional metal with large effective
charge carrier mass . Spanning the entire range of the semiconductor-metal
crossover, we observed an almost constant enhancement of the measured
thermopower compared to that estimated by the classical theory of electron
diffusion. Using the latter for a quantitative description one has to employ an
enhancement factor of 10-30. Our observations point to the importance of
electron-electron correlations in the thermal transport of FeSb, and
suggest a route to design thermoelectric materials for cryogenic applications.Comment: 3 pages, 3 figures, accepted for publication in Appl. Phys. Lett.
(2011
Challenge on the Astrophysical R-process Calculation with Nuclear Mass Models
Our understanding of the rapid neutron capture nucleosynthesis process in
universe depends on the reliability of nuclear mass predictions. Initiated by
the newly developed mass table in the relativistic mean field theory (RMF), in
this paper the influence of mass models on the -process calculations is
investigated assuming the same astrophysical conditions. The different model
predictions on the so far unreachable nuclei lead to significant deviations in
the calculated r-process abundances.Comment: 3 pages, 3 figure
Observing collapse in two colliding dipolar Bose-Einstein condensates
We study the collision of two Bose-Einstein condensates with pure dipolar
interaction. A stationary pure dipolar condensate is known to be stable when
the atom number is below a critical value. However, collapse can occur during
the collision between two condensates due to local density fluctuations even if
the total atom number is only a fraction of the critical value. Using full
three-dimensional numerical simulations, we observe the collapse induced by
local density fluctuations. For the purpose of future experiments, we present
the time dependence of the density distribution, energy per particle and the
maximal density of the condensate. We also discuss the collapse time as a
function of the relative phase between the two condensates.Comment: 6 pages, 7 figure
Dynamics of a two-species Bose-Einstein condensate in a double well
We study the dynamics of a two-species Bose-Einstein condensate in a double
well. Such a system is characterized by the intraspecies and interspecies
s-wave scattering as well as the Josephson tunneling between the two wells and
the population transfer between the two species. We investigate the dynamics
for some interesting regimes and present numerical results to support our
conclusions. In the case of vanishing intraspecies scattering lengths and a
weak interspecies scattering length, we find collapses and revivals in the
population dynamics. A possible experimental implementation of our proposal is
briefly discussed.Comment: 7 pages, 5 figure
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