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A weak localisation theory for a semiconductor quantum wire, which has a width of the order of the Fermi wavelength is presented. In the model the electronic motion is essentially one-dimensional and the localisation length L1 is much larger than the mean free path l, so that, in contrast to conventional theories a non-localised quantum wire with a total length Lproperties, the authors study the temperature dependence and the subbands effect of the weak localisation. They find that when (the phase coherent length) Lphi>L, the conductance of the quantum wire depends on L instead of Lphi, implying a temperature independent behaviour. The theory explains recent experiments which found temperature independent transport behaviour at very low temperature for narrow AlGaAs/GaAs quantum wire. In studying the AC conductivity, the calculation predicts that, for the quantum wire with L>L1, there exists a critical value of the frequency above which the system is delocalised and the AC conductivity sigma ( omega ) rises as omega 2.

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Journal of Physics: Condensed Matter

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