Spin and interaction effects on charge distribution and currents in one-dimensional conductors and rings within the Hartree-Fock approximation

Using the self--consistent Hartree-Fock approximation for electrons with spin at zero temperature, we study the effect of the electronic interactions on the charge distribution in a one-dimensional continuous ring containing a single $\delta$ scatterer. We reestablish that the interaction suppresses the decay of the Friedel oscillations. Based on this result, we show that in an infinite one dimensional conductor containing a weak scatterer, the current is totally suppressed because of a gap opened at the Fermi energy. In a canonical ensemble of continuous rings containing many scatterers, the interactions enhance the average and the typical persistent current.Comment: 5 pages, 4 figure

The interplay between electron-electron interactions and impurities in one-dimensional rings

The persistent current and charge stiffness of a one-dimensional Luttinger liquid on a ring threaded by a magnetic flux are calculated by Monte Carlo simulation. By changing the random impurity potential strength and the electron-electron interaction, we see a crossover behavior between weak and strong impurity limits. For weak impurity potentials, interactions enhance impurity effects, that is, interactions decrease the current and the stiffness. On the other hand, interactions tend to screen impurities when the impurity potential is strong. Temperature dependence of the persistent current and the charge stiffness shows a peak at a characteristic temperature, consistent with a recent single impurity study.Comment: 4 pages (ReVTeX3.0) + 3 figures (in uuencoded postscript format) appended in the end of the fil

Enhanced Charge and Spin Currents in the One-Dimensional Disordered Mesoscopic Hubbard Ring

We consider a one-dimensional mesoscopic Hubbard ring with and without disorder and compute charge and spin stiffness as a measure of the permanent currents. For finite disorder we identify critical disorder strength beyond which the charge currents in a system with repulsive interactions are {\em larger} than those for a free system. The spin currents in the disordered repulsive Hubbard model are enhanced only for small $U$, where the magnetic state of the system corresponds to a charge density wave pinned to the impurities. For large $U$, the state of the system corresponds to localized isolated spins and the spin currents are found to be suppressed. For the attractive Hubbard model we find that the charge currents are always suppressed compared to the free system at all length scales.Comment: 20 RevTeX 3.0 pages, 8 figures NOT include

Interacting electrons in disordered potentials: Conductance versus persistent currents

An expression for the conductance of interacting electrons in the diffusive regime as a function of the ensemble averaged persistent current and the compressibility of the system is presented. This expression involves only ground-state properties of the system. The different dependencies of the conductance and persistent current on the electron-electron interaction strength becomes apparent. The conductance and persistent current of a small system of interacting electrons are calculated numerically and their variation with the strength of the interaction is compared. It is found that while the persistent current is enhanced by interactions, the conductance is suppressed.Comment: REVTeX, 4 pages, 3 figures, all uuencoded, accepted for publication in PR

Does the attractive Hubbard model support larger persistent currents than the repulsive one ?

We consider a one-dimensional Hubbard model in the presence of disorder. We compute the charge stiffness for a mesoscopic ring, as a function of the size $L$, which is a measure of the permanent currents. We find that for finite disorder the permanent currents of the system with repulsive interactions are larger than those of the system with attractive interactions. This counter intuitive result is due to the fact that local density fluctuations are reduced in the presence of repulsive interactions.Comment: 14 pages; Revtex 3.0; 3 postscript figures uuencoded with uufile

Short-range repulsion and isospin dependence in the KN system

The short-range properties of the KN interaction are studied within the meson-exchange model of the Juelich group. Specifically, dynamical explanations for the phenomenological short-range repulsion, required in this model for achieving agreement with the empirical KN data, are explored. Evidence is found that contributions from the exchange of a heavy scalar-isovector meson (a_0(980)) as well as from genuine quark-gluon exchange processes are needed. Taking both mechanisms into account a satisfactory description of the KN phase shifts can be obtained without resorting to phenomenological pieces.Comment: 26 pages, 5 figure

Kaon effective mass and energy from a novel chiral SU(3)-symmetric Lagrangian

A new chiral SU(3) Lagrangian is proposed to describe the properties of kaons and antikaons in the nuclear medium, the ground state of dense matter and the kaon-nuclear interactions consistently. The saturation properties of nuclear matter are reproduced as well as the results of the Dirac-Br\"{u}ckner theory. Our numerical results show that the kaon effective mass might be changed only moderately in the nuclear medium due to the highly non-linear density effects. After taking into account the coupling between the omega meson and the kaon, we obtain similar results for the effective kaon and antikaon energies as calculated in the one-boson-exchange model while in our model the parameters of the kaon-nuclear interactions are constrained by the SU(3) chiral symmetry.Comment: 13 pages, Latex, 3 PostScript figures included; replaced by the revised version, to appear in Phys. Rev.

K−K^- - nucleus relativistic mean field potentials consistent with kaonic atoms

$K^-$ atomic data are used to test several models of the $K^-$ nucleus interaction. The t($\rho$)$\rho$ optical potential, due to coupled channel models incorporating the $\Lambda$(1405) dynamics, fails to reproduce these data. A standard relativistic mean field (RMF) potential, disregarding the $\Lambda$(1405) dynamics at low densities, also fails. The only successful model is a hybrid of a theoretically motivated RMF approach in the nuclear interior and a completely phenomenological density dependent potential, which respects the low density theorem in the nuclear surface region. This best-fit $K^-$ optical potential is found to be strongly attractive, with a depth of 180 \pm 20 MeV at the nuclear interior, in agreement with previous phenomenological analyses.Comment: revised, Phys. Rev. C in pres

Effects of disorder on two strongly correlated coupled chains

We study the effects of disorder on a system of two coupled chain of strongly correlated fermions (ladder system), using renormalization group. The stability of the phases of the pure system is investigated as a function of interactions both for fermions with spin and spinless fermions. For spinless fermions the repulsive side is strongly localized whereas the system with attractive interactions is stable with respect to disorder, at variance with the single chain case. For fermions with spins, the repulsive side is also localized, and in particular the d-wave superconducting phase found for the pure system is totally destroyed by an arbitrarily small amount of disorder. On the other hand the attractive side is again remarkably stable with respect to localization. We have also computed the charge stiffness, the localization length and the temperature dependence of the conductivity for the various phases. In the range of parameter where d-wave superconductivity would occur for the pure system the conductivity is found to decrease monotonically with temperature, even at high temperature, and we discuss this surprising result. For a model with one site repulsion and nearest neighbor attraction, the most stable phase is an orbital antiferromagnet . Although this phase has no divergent superconducting fluctuation it can have a divergent conductivity at low temperature. We argue based on our results that the superconductivity observed in some two chain compounds cannot be a simple stabilization of the d-wave phase found for a pure single ladder. Applications to quantum wires are discussed.Comment: 47 pages, ReVTeX , 8 eps figures submitted to PR

Coulomb drag in mesoscopic rings

We develop a Luttinger liquid theory of the Coulomb drag of persistent currents flowing in concentric mesoscopic rings, by incorporating non-linear corrections to the electron dispersion relation. We demonstrate that at low temperatures, interactions between electrons in different rings generate an additional phase and thus alter the period of Aharonov-Bohm oscillations. The resulting nondissipative drag depends strongly on the relative parity of the electron numbers. We also show that interactions set a new temperature scale below which the linear response theory does not apply at certain values of external flux.Comment: Latex 10 pages + 2 Figure