Strong localization of electrons in quasi-one-dimensional conductors

Abstract

We report on the experimental study of electron transport in sub-micron-wide "wires" fabricated from Si δ-doped GaAs. These quasi-one-dimensional (Q1D) conductors demonstrate the crossover from weak to strong localization with decreasing the temperature. On the insulating side of the crossover, the resistance has been measured as a function of temperature, magnetic field, and applied voltage for different values of the electron concentration, which was varied by applying the gate voltage. The activation temperature dependence of the resistance has been observed with the activation energy close to the mean energy spacing of electron states within the localization domain. The study of non-linearity of the current-voltage characteristics provides information on the distance between the critical hops which govern the resistance of Q1D conductors in the strong localization (SL) regime. We observe the exponentially strong negative magnetoresistance; this orbital magnetoresistance is due to the universal magnetic-field dependence of the localization length in Q1D conductors. The method of measuring of the single-particle density of states (DoS) in the SL regime has been suggested. Our data indicate that there is a minimum of DoS at the Fermi level due to the long-range Coulomb interaction.

Cotunneling and one-dimensional localization in individual disordered single-wall carbon nanotubes: Temperature dependence of the intrinsic resistance

“…A rough estimate of the number of barriers N can be made by taking N =1/␣, which assumes identical barriers. 21 In this way we obtain N Շ 20. Figure 3͑a͒ shows the effect of the gate voltage, which controls the position of the Fermi level in the tube.…”

“…Similar R͑T͒ behaviors have been reported for disordered wires microfabricated in semiconductors. 21,22 Figures 1͑f͒-1͑h͒ show R͑T͒ measurements on other tubes. Some of them deviate from the standard activated behavior.…”

Transition from Coulomb blockade to insulator regime in multiwall carbon nanotubes

“…Above the critical voltage, the samples come back abruptly to the scaling behaviour and each curve (corresponding to different temperatures) aligns itself on the scaling law function (represented in black discontinued curves). These two different states can be understood as follows: For low voltage values such as V < V C , the sample resistance is governed by the resistance of typical break region without localized states [18,19], which manifests by an insulating state with high resistance. By increasing the voltage, each critical hop see its activation decreasing proportionally [17][18][19].…”

Localization under the effect of randomly distributed decoherence

“…Experiments on various nanosystems have been performed, see e.g. [32][33][34][35][36], where a transition from Ohmic to exponential behavior is observed. It is found [32] that this transition occurs when the phase coherence length approaches the localization length 2 , which agrees with our condition (17).…”