Persistent currents in diffusive metallic cavities: Large values and anomalous scaling with disorder

The effect of disorder on confined metallic cavities with an Aharonov-Bohm flux line is addressed. We find that, even deep in the diffusive regime, large values of persistent currents may arise for a wide variety of geometries. We present numerical results supporting an anomalous scaling law of the average typical current $$ with the strength of disorder $w$, $\sim w^{- \gamma}$ with $\gamma < 2$. This is contrasted with previously reported results obtained for cylindrical samples where a scaling $\sim w^{-2}$ has been found. Possible links to, up to date, unexplained experimental data are finally discussed.Comment: 5 pages, 4 figure

Generation of spin-polarized currents in Zeeman-split Tomonaga-Luttinger models

In a magnetic field an interacting electron gas in one dimension may be described as a Tomonaga-Luttinger model comprising two components with different Fermi velocities due to the Zeeman splitting. This destroys the spin-charge separation, and even the quantities such as the density-density correlation involve spin and charge critical exponents (K). Specifically, the ratio of the up-spin and down-spin conductivities in a dirty system diverges at low temperatures like an inverse power of the temperature, $T^{-(K_{\uparrow}-K_{\downarrow})}$, resulting in a spin-polarized current. In finite, clean systems the conductance becomes different for up- and down-spins as another manifestation of the electron-electron interaction.Comment: 10 pages, RevTeX file, 3 figures available on request from [email protected]

Limits on the production of scalar leptoquarks from Z (0) decays at LEP

A search has been made for pairs and for single production of scalar leptoquarks of the first and second generations using a data sample of 392000 Z0 decays from the DELPHI detector at LEP 1. No signal was found and limits on the leptoquark mass, production cross section and branching ratio were set. A mass limit at 95% confidence level of 45.5 GeV/c2 was obtained for leptoquark pair production. The search for the production of a single leptoquark probed the mass region above this limit and its results exclude first and second generation leptoquarks D0 with masses below 65 GeV/c2 and 73 GeV/c2 respectively, at 95% confidence level, assuming that the D0lq Yukawa coupling alpha(lambda) is equal to the electromagnetic one. An upper limit is also given on the coupling alpha(lambda) as a function of the leptoquark mass m(D0)

Conductance through two quantum dots in a ring: Magnetic flux dependence

The conductance of a double-dot system in a ring threaded by a magnetic flux is studied. The ring is connected to two leads in such a way that each dot is embedded in one arm of the structure. The currents going through each arm of the ring are determined by the Aharonov-Bohm effect and the dot charging effects. The conductance for different values of the magnetic flux is obtained as a function of the gate potentials applied to the dots, for two situations: when the dot level energies are equal, ΔE = 0, and when they are different but with ΔE smaller than the Coulomb interaction U. The conductance shows quite distinct behavior according to having a finite or zero magnetic flux threading the ring. The system presents S = 1/2 and S = l Kondo phenomena for no magnetic flux and is in the S = 1/2 Kondo regime in the case of half a quantum of magnetic flux.Fil:Apel, V.M. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina

Electroweak measurements in electron–positron collisions at w-boson-pair energies at lep

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