CROSSOVER FROM WEAK TO STRONG LOCALIZATION IN QUASI-ONE-DIMENSIONAL CONDUCTORS

The crossover from weak to strong localization in the resistance of qu asi-1D conductors is observed for the first time with decreasing the t emperature; it occurs when the phase-breaking length becomes comparabl e with the localization length. The signature of the strong-localizati on regime is an activation-type temperature dependence of the resistan ce and exponentially strong negative magnetoresistance. The magnetores istance is well described by the theory of doubling of the localizatio n length in quasi-1D conductors in strong fields; this provides a dire ct measurement of the localization length.