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Paper   IPM / Physic / 8853
School of Physics
  Title:   Metal-Insulator Transition in Random Superlattices with Long-Range Correlated Disorder
1.  A. Esmailpour
2.  P. Carpena
3.  M.R. Rahimi Tabar
  Status:   In Proceedings
  Proceeding: Condensed Matter Physics Conference of Balkan Countries, Mugla University , Mugla , TURKEY, 26 - 28 May, 2008
  Year:  2008
  Supported by:  IPM
It is known that all electron states in uncorrelated disordered one dimensional system are exponentially localized [1]. In recent years, a number of models [2-4] have predicted the existence of extended states for disordered one-dimensional systems with short and long range correlations. In this paper, we study the electronic properties of disordered GaAs-AlGaAs semiconductor superlattices with structural long-range correlations. The system consists of quantum barriers and wells with different thicknesses and heights which fluctuate around their mean values randomly, following a long-range correlated pattern of fractal type characterized by a power spectrum of the type , where the exponent S(K) ∝ 1/k(2α−1) quantifies the strength of the long-range correlations [5]. For a given system size, we find a critical value of the exponent a acfor which a metal-insulator transition appears: for a < ac all the states are localized, and for a\succ ac, we find a continuous band of extended states. We also show that the existence of extended states causes a strong enhancement of the DC conductance of the superlattice at finite temperature, which increases in many orders of magnitude when crossing from the localized to the extended regime. Finally, we perform finite size scaling and we obtain the value of the critical exponent c��in the thermodynamic limit, showing that the transition is not a finite-size effect.

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