9,544 research outputs found
Stripe Formation in Fermionic Atoms on 2-D Optical Lattice inside a Box Trap: DMRG Studies for Repulsive Hubbard Model with Open Boundary Condition
We suggest that box shape trap enables to observe intrinsic properties of the
repulsive Hubbard model in a fixed doping in contrast to the harmonic trap
bringing about spatial variations of atom density profiles. In order to predict
atomic density profile under the box trap, we apply the directly-extended
density-matrix renormalization group method to 4-leg repulsive Hubbard model
with the open boundary condition. Consequently, we find that stripe formation
is universal in a low hole doping range and the stripe sensitively changes its
structure with variations of and the doping rate. A remarkable change is
that a stripe formed by a hole pair turns to one by a bi-hole pair when
entering a limited strong range. Furthermore, a systematic calculation
reveals that the Hubbard model shows a change from the stripe to the Friedel
like oscillation with increasing the doping rate
Effect of the Zero-Mode on the Response of a Trapped Bose-Condensed Gas
The dynamical response of a trapped Bose-Einstein condensate (BEC) is
formulated consistently with quantum field theory and is numerically evaluated.
We regard the BEC as a manifestation of the breaking of the global phase
symmetry. Then, the Goldstone theorem implies the existence of a zero energy
excitation mode (the zero-mode). We calculate the effect of the zero-mode on
the response frequency and show that the contribution of the zero-mode to the
first excitation mode is not so important in the parameter set realized in the
existing experiment. This is the reason that experimental results can be
described using the Bogoliubov prescription, although it breaks the consistency
of the description in quantum field theory.Comment: 18 pages, 3 figure
Infrared diode laser spectroscopy of the fundamental band of NF(a1Δ)
Thirty-one lines of the fundamental vibration–rotation band of the NF free radical in its a 1 state have been detected in absorption near 8.6 µm using a tunable infrared diode laser. Linewidths were Doppler limited and several transitions were accompanied by resolved hyperfine structure due to fluorine and nitrogen nuclear moments. Wave number calibration using accurately determined N2O lines yielded v0 = 1165.952±0.001 cm^−1 for the band center. Rotational and centrifugal distortion constants for both v = 0 and 1 states have also been determined
The vibrational predissociation spectroscopy of hydrogen cluster ions
The first infrared spectra of protonated hydrogen clusters in the gas phase have been observed. Predissociation spectra were taken with a tandem mass spectrometer: mass selected hydrogen cluster ions were irradiated inside a rf ion trap by a tunable infrared laser, and the fragment ions created by photodissociation of the clusters were mass selected and detected. Spectra for each product channel were measured by counting fragment ions as a function of laser frequency. Low resolution spectra (Deltanu=10 cm^−1) in the region from 3800 to 4200 cm^−1 were observed for the ions H + 5, H + 7, and H + 9 at 3910, 3980, and 4020 cm−1, respectively. A band was also observed for H + 5 at 3532 cm^−1. No rotational structure was resolved. The frequencies of the band maxima agree well with the frequencies predicted by previous ab initio calculations for the highest modes
Magnetism Localization in Spin-Polarized One-Dimensional Anderson-Hubbard Model
In order to study an interplay of disorder, correlation, and spin imbalance
on antiferromagnetism, we systematically explore the ground state of
one-dimensional spin-imbalanced Anderson-Hubbard model by using the
density-matrix renormalization group method. We find that disorders localize
the antiferromagnetic spin density wave induced by imbalanced fermions and the
increase of the disorder magnitude shrinks the areas of the localized
antiferromagnetized regions. Moreover, the antiferromagnetism finally
disappears above a large disorder. These behaviors are observable in atomic
Fermi gases loaded on optical lattices and disordered strongly-correlated
chains under magnetic field
Quantum Field Theoretical Analysis on Unstable Behavior of Bose-Einstein Condensates in Optical Lattices
We study the dynamics of Bose-Einstein condensates flowing in optical
lattices on the basis of quantum field theory. For such a system, a
Bose-Einstein condensate shows a unstable behavior which is called the
dynamical instability. The unstable system is characterized by the appearance
of modes with complex eigenvalues. Expanding the field operator in terms of
excitation modes including complex ones, we attempt to diagonalize the
unperturbative Hamiltonian and to find its eigenstates. It turns out that
although the unperturbed Hamiltonian is not diagonalizable in the conventional
bosonic representation the appropriate choice of physical states leads to a
consistent formulation. Then we analyze the dynamics of the system in the
regime of the linear response theory. Its numerical results are consitent with
as those given by the discrete nonlinear Schrodinger equation.Comment: 16pages, 4figure
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