5,328 research outputs found
Electronic State and Magnetic Susceptibility in Orbitally Degenerate (J=5/2) Periodic Anderson Model
Magnetic susceptibility in a heavy fermion systemis composed of the Pauli
term (\chi_P) and the Van-Vleck term (\chi_V). The latter comes from the
interband excitation, where f-orbital degeneracy is essential. In this work, we
study \chi_P and \chi_V in the orbitally degenerate (J=5/2) periodic Anderson
model for both the metallic and insulating cases. The effect of the correlation
between f-electrons is investigated using the self-consistent second-order
perturbation theory. The main results are as follows. (i) Sixfold degenerate
model: both \chi_P and \chi_V are enhanced by a factor of 1/z (z is the
renormalization constant). (ii) Nondegenerate model: only \chi_P is enhanced by
1/z. Thus, orbital degeneracy is indispensable for enhancement of \chi_V.
Moreover, orbital degeneracy reduces the Wilson ratio and stabilizes a
nonmagnetic Fermi liquid state.Comment: 4 pages, revtex, to be published in J. Phys. Soc. Jpn. (No.8
Josephson Current between Triplet and Singlet Superconductors
The Josephson effect between triplet and singlet superconductors is studied.
Josephson current can flow between triplet and singlet superconductors due to
the spin-orbit coupling in the spin-triplet superconductor but it is finite
only when triplet superconductor has , where and
are the perpendicular components of orbital angular momentum and spin angular
momentum of the triplet Cooper pairs, respectively. The recently observed
temperature and orientational dependence of the critical current through a
Josephson junction between UPt and Nb is investigated by considering a
non-unitary triplet state.Comment: 4 pages, no figure
Deformation of Quantum Dots in the Coulomb Blockade Regime
We extend the theory of Coulomb blockade oscillations to quantum dots which
are deformed by the confining potential. We show that shape deformations can
generate sequences of conductance resonances which carry the same internal
wavefunction. This fact may cause strong correlations of neighboring
conductance peaks. We demonstrate the relevance of our results for the
interpretation of recent experiments on semiconductor quantum dots.Comment: 4 pages, Revtex, 4 postscript figure
Pseudogap Formation in the Symmetric Anderson Lattice Model
We present self-consistent calculations for the self-energy and magnetic
susceptibility of the 2D and 3D symmetric Anderson lattice Hamiltonian, in the
fluctuation exchange approximation. At high temperatures, strong f-electron
scattering leads to broad quasiparticle spectral functions, a reduced
quasiparticle band gap, and a metallic density of states. As the temperature is
lowered, the spectral functions narrow and a pseudogap forms at the
characteristic temperature at which the width of the quasiparticle
spectral function at the gap edge is comparable to the renormalized activation
energy. For , the pseudogap is approximately equal to the
hybridization gap in the bare band structure. The opening of the pseudogap is
clearly apparent in both the spin susceptibility and the compressibility.Comment: RevTeX - 14 pages and 7 figures (available on request),
NRL-JA-6690-94-002
Superfluidity in the interior-gap states
We investigate superfluidity in the interior-gap states proposed by Liu and
Wilczek. At weak coupling, we find the {\em gapless} interior-gap state
unstable in physically accessible regimes of the parameter space, where the
superfluid density is shown to be always negative. We therefore conclude that
the spatially-uniform interior-gap phase is extremely unstable unless it is
fully gapped; in this case, however, the state is rather similar to
conventional BCS states.Comment: To appear in Physical Review
Energy Resolved Supercurrent between two superconductors
In this paper I study the energy resolved supercurrent of a junction
consisting of a dirty normal metal between two superconductors. I also consider
a cross geometry with two additional arms connecting the above mentioned
junction with two normal reservoirs at equal and opposite voltages. The
dependence of the supercurrent between the two superconductors on the applied
voltages is studied.Comment: revtex, 7 pages, 8 figures. accepted by Phys. Rev.
Magnetic Field Effect on the Supercurrent of an SNS junction
In this paper we study the effect of a Zeeman field on the supercurrent of a
mesoscopic SNS junction. It is shown that the supercurrent suppression is due
to a redistribution of current-carrying states in energy space. A dramatic
consequence is that (part of the) the suppressed supercurrent can be recovered
with a suitable non-equilibrium distribution of quasiparticles.Comment: 4 figures in postscrip
Immunologic Response to Antiretroviral Therapy in Hepatitis C Virus-Coinfected Adults in a Population-Based HIV/AIDS Treatment Program
BackgroundWe sought to characterize the impact that hepatitis C virus (HCV) infection has on CD4 cells during the first 48 weeks of antiretroviral therapy (ART) in previously ART-naive human immunodeficiency virus (HIV)-infected patients MethodsThe HIV/AIDS Drug Treatment Programme at the British Columbia Centre for Excellence in HIV/AIDS distributes all ART in this Canadian province. Eligible individuals were those whose first-ever ART included 2 nucleoside reverse transcriptase inhibitors and either a protease inhibitor or a nonnucleoside reverse transcriptase inhibitor and who had a documented positive result for HCV antibody testing. Outcomes were binary events (time to an increase of ⩾75 CD4 cells/mm3 or an increase of ⩾10% in the percentage of CD4 cells in the total T cell population [CD4 cell fraction]) and continuous repeated measures. Statistical analyses used parametric and nonparametric methods, including multivariate mixed-effects linear regression analysis and Cox proportional hazards analysis ResultsOf 1186 eligible patients, 606 (51%) were positive and 580 (49%) were negative for HCV antibodies. HCV antibody-positive patients were slower to have an absolute (P<.001) and a fraction (P=.02) CD4 cell event. In adjusted Cox proportional hazards analysis (controlling for age, sex, baseline absolute CD4 cell count, baseline pVL, type of ART initiated, AIDS diagnosis at baseline, adherence to ART regimen, and number of CD4 cell measurements), HCV antibody-positive patients were less likely to have an absolute CD4 cell event (adjusted hazard ratio [AHR], 0.84 [95% confidence interval {CI}, 0.72-0.98]) and somewhat less likely to have a CD4 cell fraction event (AHR, 0.89 [95% CI, 0.70-1.14]) than HCV antibody-negative patients. In multivariate mixed-effects linear regression analysis, HCV antibody-negative patients had increases of an average of 75 cells in the absolute CD4 cell count and 4.4% in the CD4 cell fraction, compared with 20 cells and 1.1% in HCV antibody-positive patients, during the first 48 weeks of ART, after adjustment for time-updated pVL, number of CD4 cell measurements, and other factors ConclusionHCV antibody-positive HIV-infected patients may have an altered immunologic response to AR
Center of mass and relative motion in time dependent density functional theory
It is shown that the exchange-correlation part of the action functional
in time-dependent density functional theory , where
is the time-dependent density, is invariant under the
transformation to an accelerated frame of reference , where is an arbitrary
function of time. This invariance implies that the exchange-correlation
potential in the Kohn-Sham equation transforms in the following manner:
. Some of the
approximate formulas that have been proposed for satisfy this exact
transformation property, others do not. Those which transform in the correct
manner automatically satisfy the ``harmonic potential theorem", i.e. the
separation of the center of mass motion for a system of interacting particles
in the presence of a harmonic external potential. A general method to generate
functionals which possess the correct symmetry is proposed
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