Observation of a discontinuous transition from strong to weak localization in 1D granular metal wires

We have studied the transition from strong to weak localization in in situ grown granular metal wires of Sn, Pb, Pb0.85Bi0.15,Ag, and Au with widths as small as 400 Angstrom. In our wires we observe a transition dramatically different from that seen in 2D films. The wires exhibit an abrupt drop in resistance as large as 4 orders of magnitude. Within this resistance ''gap'' no stable wire is observed. We speculate that we are observing a first order electronic phase transition between the strongly localized and weakly localized states.