Electron Dephasing in Mesoscopic Metal Wires

The low-temperature behavior of the electron phase coherence time, τφ, in mesoscopic metal wires has been a subject of controversy recently. Whereas theory predicts that τφ(T ) in narrow wires should increase as T as the temperature T is lowered, many samples exhibit a saturation of τφ 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 τφ down to our base temperature of 40 mK. In addition, the measured magnitude of τφ is in excellent quantitative agreement with the prediction of the perturbative theory of Altshuler, Aronov and Khmelnitskii. We discuss possible explanations why saturation of τφ 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.