Temperature dependent weak localization is measured in metallic nanowires in a previously unexplored 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 ($\tau_{ \phi} \sim T^{ -2/3}$) in the narrowest wires, but exhibits a relative saturation as $T \to 0$ 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.
Categories: cond-mat.mes-hall cond-mat.dis-nn