25 research outputs found
Trapped Atomic Fermi Gases
A many-body system of fermion atoms with a model interaction characterized by
the scattering length is considered. We treat both and the density as
parameters assuming that the system can be created artificially in a trap. If
is negative the system becomes strongly correlated at densities , provided the scattering length is the dominant parameter of the
problem. It means that we consider to be much bigger than the radius of
the interaction or any other relevant parameter of the system. The density
at which the compressibility vanishes is defined by . Thus, a system composed of fermion atoms with the scattering length
is completely unstable at low densities, inevitably collapsing
until the repulsive core stops the density growth. As a result, any Fermi
system possesses the equilibrium density and energy if the bare
particle-particle interaction is sufficiently strong to make negative and
to be the dominant parameter. This behavior can be realized in a trap. Our
results show that a low density neutron matter can have the equilibrium
density.Comment: 6 pages, to be published in Physics Letters
Novel Electron Spectroscopy of Tenuously and Weakly Bound Negative Ions
A novel method is proposed that uses very slow electron elastic collisions
with atoms to identify their presence through the observation of tenuously
bound (electron impact energy, E<0.1 eV) and weakly bound (E<1 eV) negative
ions, formed as Regge resonances during the collisions.Comment: 4pages, 3figure
On the relation between the Hartree-Fock and Kohn-Sham approaches
We show that the Hartree-Fock (HF) results cannot be reproduced within the
framework of Kohn-Sham (KS) theory because the single-particle densities of
finite systems obtained within the HF calculations are not -representable,
i.e., do not correspond to any ground state of a non-interacting electron
systems in a local external potential. For this reason, the KS theory, which
finds a minimum on a different subset of all densities, can overestimate the
ground state energy, as compared to the HF result. The discrepancy between the
two approaches provides no grounds to assume that either the KS theory or the
density functional theory suffers from internal contradictions.Comment: 7 pages, ReVtex, revised and accepted by Physics Letters
Energy scales and magnetoresistance at a quantum critical point
The magnetoresistance (MR) of CeCoIn_5 is notably different from that in many
conventional metals. We show that a pronounced crossover from negative to
positive MR at elevated temperatures and fixed magnetic fields is determined by
the scaling behavior of quasiparticle effective mass. At a quantum critical
point (QCP) this dependence generates kinks (crossover points from fast to slow
growth) in thermodynamic characteristics (like specific heat, magnetization
etc) at some temperatures when a strongly correlated electron system transits
from the magnetic field induced Landau Fermi liquid (LFL) regime to the
non-Fermi liquid (NFL) one taking place at rising temperatures. We show that
the above kink-like peculiarity separates two distinct energy scales in QCP
vicinity - low temperature LFL scale and high temperature one related to NFL
regime. Our comprehensive theoretical analysis of experimental data permits to
reveal for the first time new MR and kinks scaling behavior as well as to
identify the physical reasons for above energy scales.Comment: 7 pages, 6 figure
Self-intersecting Regge trajectories in multi-channel scattering
We present a simple direct method for calculating Regge trajectories for a
multichannel scattering problem. The approach is applied to the case of two
coupled Thomas-Fermi type potentials, used as a crude model for electron-atom
scattering below the second excitation threshold. It is shown that
non-adiabatic interaction may cause formation of loops in Regge trajectories.
The accuracy of the method is tested by evaluating resonance contributions to
elastic and inelastic integral cross sections.Comment: 5 pages, 4 figure
Quasiparticles and order parameter near quantum phase transition in heavy fermion metals
It is shown that the Landau paradigm based upon both the quasiparticle
concept and the notion of the order parameter is valid and can be used to
explain the anomalous behavior of the heavy fermion metals near quantum
critical points. The understanding of this phenomenon has been problematic
largely because of the absence of theoretical guidance. Exploiting this
paradigm and the fermion condensation quantum phase transition, we investigate
the anomalous behavior of the heavy electron liquid near its critical point at
different temperatures and applied magnetic fields. We show that this anomalous
behavior is universal and can be used to capture the essential aspects of
recent experiments on heavy-fermion metals at low temperatures.Comment: 14 pages, revised and accepted by Physics Letters
Photoabsorption spectrum of the Xe@C
Photoabsorption spectrum of the Xe@C60 endohedral fullerene has been studied
using the time-dependent-density-functional-theory (TDDFT), which represents the dynamical
polarizability of an interacting electron system by an off-diagonal matrix element of the
resolvent of the Liouvillian superoperator and solves the problem with the Lanczos
algorithm. The method has been tested with the photoabsorption spectra for the free Xe
atom and C60 fullerene. The result of the Xe atom encapsulated inside
C60 confirms the three main peaks observed in the recent measurement in the
energy region of the Xe 4d giant resonance and indicates the possibility
that the Auger decay of the Xe+ has been greatly suppressed if the ion is
encapsulated inside C60. It is suggested to use the current theoretical result
around 22 eV to check this possibility
Photoionization of the Xe atom and Xe@C
Photoionization of the Xe atom and Xe@C60 molecule have been studied using
the random phase approximation with exchange (RPAE) method. The Xe atom was described by
relaxed orbitals including overlap integrals. The C60 fullerene has been
represented by an attractive short range spherical well with potential
V(r), given by
V(r) = −V0 for
ri < r < ro,
otherwise V(r) = 0 where
ri and
ro are respectively, the inner and outer
radii of the spherical shell. The time independent Schrödinger equation was solved using
both regular and irregular solutions and the continuous boundary conditions at
ri and
ro. The results demonstrate improvement
to previous calculations for both the Xe atom and Xe@C60 molecule and compare
very well with the recent experimental data