Hopping models and ac universality

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    Abstrakt

    Some general relations for hopping models are established. We proceed to discuss the universality of the ac conductivity which arises in the extreme disorder limit of the random barrier model. It is shown that the relevant dimension entering into the diffusion cluster approximation (DCA) is the harmonic (fracton) dimension of the diffusion cluster. The temperature scaling of the dimensionless frequency entering into the DCA is discussed. Finally, some open problems regarding ac universality are listed.
    OriginalsprogEngelsk
    TidsskriftIPPS physica status solidi (b)
    Vol/bind230
    Udgave nummer1
    Sider (fra-til)5-13
    ISSN0370-1972
    StatusUdgivet - 2002

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