726 research outputs found
Two-dimensional boson-fermion mixtures
Using mean-field theory, we study the equilibrium properties of boson-fermion
mixtures confined in a harmonic pancake-shaped trap at zero temperature. When
the modulus of the s-wave scattering lengths are comparable to the mixture
thickness, two-dimensional scattering events introduce a logarithmic dependence
on density in the coupling constants, greatly modifying the density profiles
themselves. We show that for the case of a negative boson-fermion
three-dimensional s-wave scattering length, the dimensional crossover
stabilizes the mixture against collapse and drives it towards spatial demixing.Comment: 9 pages, 4 figure
Magnetoplasmon excitations in an array of periodically modulated quantum wires
Motivated by the recent experiment of Hochgraefe et al., we have investigated
the magnetoplasmon excitations in a periodic array of quantum wires with a
periodic modulation along the wire direction. The equilibrium and dynamic
properties of the system are treated self-consistently within the
Thomas-Fermi-Dirac-von Weizsaecker approximation. A calculation of the
dynamical response of the system to a far-infrared radiation field reveals a
resonant anticrossing between the Kohn mode and a finite-wavevector
longitudinal excitation which is induced by the density modulation along the
wires. Our theoretical calculations are found to be in excellent agreement with
experiment.Comment: 9 pages, 8 figure
Exact first-order density matrix for a d-dimensional harmonically confined Fermi gas at finite temperature
We present an exact closed form expression for the {\em finite temperature}
first-order density matrix of a harmonically trapped ideal Fermi gas in any
dimension. This constitutes a much sought after generalization of the recent
results in the literature, where exact expressions have been limited to
quantities derived from the {\em diagonal} first-order density matrix. We
compare our exact results with the Thomas-Fermi approximation (TFA) and
demonstrate numerically that the TFA provides an excellent description of the
first-order density matrix in the large-N limit. As an interesting application,
we derive a closed form expression for the finite temperature Hartree-Fock
exchange energy of a two-dimensional parabolically confined quantum dot. We
numerically test this exact result against the 2D TF exchange functional, and
comment on the applicability of the local-density approximation (LDA) to the
exchange energy of an inhomogeneous 2D Fermi gas.Comment: 12 pages, 3 figures included in the text, RevTeX4. Text before
Eq.(25) corrected. Additional equation following Eq.(25) has been adde
Stability and correlations in dilute two-dimensional boson systems
The hyperspherical adiabatic expansion method is used to describe
correlations in a symmetric boson system rigorously confined to two spatial
dimensions. The hyperangular eigenvalue equation turns out to be almost
independent of the hyperradius, whereas the solutions are strongly varying with
the strength of the attractive two-body potentials. Instability is encountered
in hyperangular, hyperradial, and mean-field equations for almost identical
strengths inversely proportional to the particle number. The derived conditions
for stability are similar to mean-field conditions and closely related to the
possible occurrence of the Thomas and Efimov effects. Renormalization in
mean-field calculations for two spatial dimensions is probably not needed.Comment: 5 pages, two figures, submitted to Phys. Rev. A, second version
contains added discussion, especially of renormalizatio
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