1,085 research outputs found
Reply to comment ``On the test of the modified BCS at finite temperature''
This is our formal Reply to revised version (v2) of arXiv: nucl-th/0510004v2.Comment: accepted in Physical Review
Quantum Size Effect in Conductivity of Multilayer Metal Films
Conductivity of quantized multilayer metal films is analyzed with an emphasis
on scattering by rough interlayer interfaces. Three different types of quantum
size effect (QSE) in conductivity are predicted. Two of these QSE are similar
to those in films with scattering by rough walls. The third type of QSE is
unique and is observed only for certain positions of the interface. The
corresponding peaks in conductivity are very narrow and high with a finite
cutoff which is due only to some other scattering mechanism or the smearing of
the interface. There are two classes of these geometric resonances. Some of the
resonance positions of the interface are universal and do not depend on the
strength of the interface potential while the others are sensitive to this
potential. This geometric QSE gradually disappears with an increase in the
width of the interlayer potential barrier.Comment: 12 pages, 10 figures, RevTeX4, to be published in Phys. Rev B (April
2003
Test of modified BCS model at finite temperature
A recently suggested modified BCS (MBCS) model has been studied at finite
temperature. We show that this approach does not allow the existence of the
normal (non-superfluid) phase at any finite temperature. Other MBCS predictions
such as a negative pairing gap, pairing induced by heating in closed-shell
nuclei, and ``superfluid -- super-superfluid'' phase transition are discussed
also. The MBCS model is tested by comparing with exact solutions for the picket
fence model. Here, severe violation of the internal symmetry of the problem is
detected. The MBCS equations are found to be inconsistent. The limit of the
MBCS applicability has been determined to be far below the ``superfluid --
normal'' phase transition of the conventional FT-BCS, where the model performs
worse than the FT-BCS.Comment: 8 pages, 9 figures, to appear in PR
Self-consistent approach for the quantum confined Stark effect in shallow quantum wells
A computationally efficient, self-consistent complex scaling approach to
calculating characteristics of excitons in an external electric field in
quantum wells is introduced. The method allows one to extract the resonance
position as well as the field-induced broadening for the exciton resonance. For
the case of strong confinement the trial function is represented in factorized
form. The corresponding coupled self-consistent equations, which include the
effective complex potentials, are obtained. The method is applied to the
shallow quantum well. It is shown that in this case the real part of the
effective exciton potential is insensitive to changes of external electric
field up to the ionization threshold, while the imaginary part has
non-analytical field dependence and small for moderate electric fields. This
allows one to express the exciton quasi-energy at some field through the
renormalized expression for the zero-field bound state.Comment: 13 pages, RevTeX4, 6 figure
Can We Apply Statistical Laws to Small Systems? the Cerium Atom
It is shown that statistical mechanics is applicable to quantum systems with
finite numbers of particles, such as complex atoms, atomic clusters, etc.,
where the residual two-body interaction is sufficiently strong. This
interaction mixes the unperturbed shell-model basis states and produces
``chaotic'' many-body eigenstates. As a result, an interaction-induced
equilibrium emerges in the system, and temperature can be introduced. However,
the interaction between the particles and their finite number can lead to
prominent deviations of the equilibrium occupation numbers distribution from
the Fermi-Dirac shape. For example, this takes place in the cerium atom with
four valence electrons, which was used to compare the theory with realistic
numerical calculations.Comment: 4 pages, Latex, two figures in eps-forma
Calculations of exchange interaction in impurity band of two-dimensional semiconductors with out of plane impurities
We calculate the singlet-triplet splitting for a couple of two-dimensional
electrons in the potential of two positively charged impurities which are
located out of plane. We consider different relations between vertical
distances of impurities and and their lateral distance . Such a
system has never been studied in atomic physics but the methods, worked out for
regular two-atomic molecules and helium atom, have been found to be useful.
Analytical expressions for several different limiting configurations of
impurities are obtained an interpolated formula for intermediate range of
parameters is proposed. The -dependence of the splitting is shown to become
weaker with increasing .Comment: 14 pages, RevTeX, 5 figures. Submitted to Phys Rev.
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