16,000 research outputs found
Interdot Coulomb repulsion effect on the charge transport of parallel double single electron transistors
The charge transport behaviors of parallel double single electron transistors
(SETs) are investigated by the Anderson model with two impurity levels. The
nonequilibrium Keldysh Green's technique is used to calculate the
current-voltage characteristics of system. For SETs implemented by quantum dots
(QDs) embedded into a thin layer, the interdot Coulomb repulsion is
more important than the interdot electron hopping as a result of high potential
barrier height between QDs and . We found that the interdot Coulomb
repulsion not onlyleads to new resonant levels, but also creates negative
differential conductances.Comment: 12 pages, 7 figure
Microscopic Restoration of Proton-Neutron Mixed Symmetry in Weakly Collective Nuclei
Starting from the microscopic low-momentum nucleon-nucleon interaction V{low
k}, we present the first systematic shell model study of magnetic moments and
magnetic dipole transition strengths of the basic low-energy one-quadrupole
phonon excitations in nearly-spherical nuclei. Studying in particular the
even-even N=52 isotones from 92Zr to 100Cd, we find the predicted evolution of
the predominantly proton-neutron non-symmetric state reveals a restoration of
collective proton-neutron mixed-symmetry structure near mid-shell. This
provides the first explanation for the existence of pronounced collective
mixed-symmetry structures in weakly-collective nuclei.Comment: 5 Pages, 3 figure
Low-momentum ring diagrams of neutron matter at and near the unitary limit
We study neutron matter at and near the unitary limit using a low-momentum
ring diagram approach. By slightly tuning the meson-exchange CD-Bonn potential,
neutron-neutron potentials with various scattering lengths such as
and are constructed. Such potentials are renormalized
with rigorous procedures to give the corresponding -equivalent
low-momentum potentials , with which the low-momentum
particle-particle hole-hole ring diagrams are summed up to all orders, giving
the ground state energy of neutron matter for various scattering lengths.
At the limit of , our calculated ratio of to that of
the non-interacting case is found remarkably close to a constant of 0.44 over a
wide range of Fermi-momenta. This result reveals an universality that is well
consistent with the recent experimental and Monte-Carlo computational study on
low-density cold Fermi gas at the unitary limit. The overall behavior of this
ratio obtained with various scattering lengths is presented and discussed.
Ring-diagram results obtained with and those with -matrix
interactions are compared.Comment: 9 pages, 7 figure
Shell model description of the 14C dating beta decay with Brown-Rho-scaled NN interactions
We present shell model calculations for the beta-decay of the 14C ground
state to the 14N ground state, treating the states of the A=14 multiplet as two
0p holes in an 16O core. We employ low-momentum nucleon-nucleon (NN)
interactions derived from the realistic Bonn-B potential and find that the
Gamow-Teller matrix element is too large to describe the known lifetime. By
using a modified version of this potential that incorporates the effects of
Brown-Rho scaling medium modifications, we find that the GT matrix element
vanishes for a nuclear density around 85% that of nuclear matter. We find that
the splitting between the (J,T)=(1+,0) and (J,T)=(0+,1) states in 14N is
improved using the medium-modified Bonn-B potential and that the transition
strengths from excited states of 14C to the 14N ground state are compatible
with recent experiments.Comment: 4 pages, 5 figures Updated to include referee comments/suggestion
Detection of hidden mineral deposits by airborne spectral analysis of forest canopies
Data from field surveys and biogeochemical tests conducted in Maine, Montana, and Washington strongly correlate with results obtained using high resolution airborne spectroradiometer which detects an anomalous spectral waveform that appears definitely associated with sulfide mineralization. The spectral region most affected by mineral stress is between 550 nm and 750 nm. Spectral variations observed in the field occur on the wings of the red chlorophyll band centered at about 690 nm. The metal-stress-induced variations on the absorption band wing are most successfully resolved in the high spectral resolution field data using a waveform analysis technique. The development of chlorophyll pigments was retarded in greenhouse plants doped with copper and zinc in the laboratory. The lowered chlorophyll production resulted in changes on the wings of the chlorophyll bands of reflectance spectra of the plants. The airborne spectroradiometer system and waveform analysis remains the most sensitive technique for biogeochemical surveys
Suppression of core polarization in halo nuclei
We present a microscopic study of halo nuclei, starting from the Paris and
Bonn potentials and employing a two-frequency shell model approach. It is found
that the core-polarization effect is dramatically suppressed in such nuclei.
Consequently the effective interaction for halo nucleons is almost entirely
given by the bare G-matrix alone, which presently can be evaluated with a high
degree of accuracy. The experimental pairing energies between the two halo
neutrons in He and Li nuclei are satisfactorily reproduced by our
calculation. It is suggested that the fundamental nucleon-nucleon interaction
can be probed in a clearer and more direct way in halo nuclei than in ordinary
nuclei.Comment: 11 pages, RevTex, 2 postscript figures; major revisions, matches
version to appear in Phys. Rev. Letter
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