Geometry-dependent dephasing in small metallic wires

Temperature dependent weak localization is measured in metallic nanowires in a previously unex plored size regime down to width w = 5 nm. The dephasing time, tau (phi), shows a low temperature T dependence close to quasi-1D theoretical expectations (tau (phi) similar to T-2/3) in the narrowest wires, but exhibits a relative saturation as T --> 0 for wide samples of the same material, as observed previously. As only sample geometry is varied to exhibit both suppression and divergence of tau (phi), this finding provides a new constraint on models of dephasing phenomena.