Electron Dephasing in Mesoscopic Metal Wires

The low-temperature behavior of the electron phase coherence time, $\tau_{\phi}$, in mesoscopic metal wires has been a subject of controversy recently. Whereas theory predicts that $\tau_{\phi}(T)$ in narrow wires should increase as $T^{-2/3}$ as the temperature $T$ is lowered, many samples exhibit a saturation of $\tau_{\phi}$ below about 1 K. We review here the experiments we have performed recently to address this issue. In particular we emphasize that in sufficiently pure Ag and Au samples we observe no saturation of $\tau_{\phi}$ down to our base temperature of 40 mK. In addition, the measured magnitude of $\tau_{\phi}$ is in excellent quantitative agreement with the prediction of the perturbative theory of Altshuler, Aronov and Khmelnitskii. We discuss possible explanations why saturation of $\tau_{\phi}$ is observed in many other samples measured in our laboratory and elsewhere, and answer the criticisms raised recently by Mohanty and Webb regarding our work.Comment: 14 pages, 3 figures; to appear in proceedings of conference "Fundamental Problems of Mesoscopic Physics", Granada, Spain, 6-11 September, 200

ULTRALOW INTERACTION TEMPERATURES AND CRYSTAL FIELD EFFECTS FOR Gd IMPURITIES IN YPd3 AND CePd3

La susceptibilité magnétique des impuretés de Gd montre que le comportement des ions est indépendant jusqu'à 10 mK si la concentration est inférieure 0.15 % dans YPd3 et inférieure à 0,5% dans CePd3. On peut expliquer ces résultats dans un modèle de champ cristallin.The magnetic susceptibility of Gd impurities shows single ion behaviour down to 10 mK at concentrations below 0.15 a/o in YPd3 and below 0.5 a/o in CePd3. The data can be fitted with crystal field theory