Influence of electron-electron scattering on spin-polarized current states in magnetic wrapped nanowires

We study the role of electron-electron collisions in the formation of spin-polarized current states in a "spin guide" which is a system consisting of a non-magnetic conducting channel wrapped in the grounded nanoscale magnetic shell. It is shown that under certain conditions the spin guide may generate and transport over long distances the non-equilibrium electron density with a high level of spin polarization, even though the frequent electron-electron scattering leads to a common drift of non-equilibrium electrons. We also propose some ways to convert the spin-polarized electron density into a spin-polarized electric current

Correlation gap in the heavy-fermion antiferromagnet UPd_2Al_3

The optical properties of the heavy-fermion compound UPd$_2$Al$_3$ have been measured in the frequency range from 0.04 meV to 5 meV (0.3 to 40 cm$^{-1}$) at temperatures $2 {\rm K}<T< 300$ K. Below the coherence temperature $T^*\approx 50$ K, the hybridization gap opens around 10 meV. As the temperature decreases further ($T\leq 20$ K), a well pronounced pseudogap of approximately 0.2 meV develops in the optical response; we relate this to the antiferromagnetic ordering which occurs below $T_N\approx 14$ K. The frequency dependent mass and scattering rate give evidence that the enhancement of the effective mass mainly occurs below the energy which is associated to the magnetic correlations between the itinerant and localized 5f electrons. In addition to this correlation gap, we observe a narrow zero-frequency conductivity peak which at 2 K is less than 0.1 meV wide, and which contains only a fraction of the delocalized carriers. The analysis of the spectral weight infers a loss of kinetic energy associated with the superconducting transition.Comment: RevTex, 15 pages, 7 figure

NONLOCAL HYDRODYNAMICS OF PHONON GAS IN INSULATORS

On a montré que le caractère des effets hydrodynamiques dans les diélectriques varie considérablement selon certaines propriétés de la loi de dispersion des vibrations transversales qui conduisent à un accroissement brusque du temps de relaxation des phonons longitudinaux de grande longueur d'onde. Les résultats obtenus permettent d'expliquer la dépendance en température des coefficients de conductibilité thermique et d'atténuation du second son que l'on observe expérimentalement.The paper shows that in case of certain properties of the transverse vibration dispersion law bringing about sharp increase of the relaxation time of longitudinal long-wave phonons (LLP), the character of hydrodynamic effects in insulators essentially changes. The results obtained permit to explain the temperature dependence of the heat conductivity and second sound attenuation coefficients observed experimentally