• Mulugeta Bekele

      Articles written in Pramana – Journal of Physics

    • Optimal barrier subdivision for Kramers’ escape rate

      Mulugeta Bekele G Ananthakrishna N Kumar

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      We examine the effect of subdividing the potential barrier along the reaction coordinate on Kramers’ escape rate for a model potential. Using the known supersymmetric potential approach, we show the existence of an optimal number of subdivisions that maximizes the rate.

    • Noise-formed triple-well potential and stochastic resonance of charge carriers

      BERHANU ARAGIE MULUGETA BEKELE GIUSEPPE PELLICANE

      More Details Abstract Fulltext PDF

      We study the thermal dynamics of charge carriers jumping across potential traps in a one-dimensional semiconductor layer. The potential traps are denser at the middle layer and decay exponentially when moving away from it. Such a distribution drives the diffusion of the charge carriers toward the centre. Then, the application of a non-uniform temperature, hotter around the centre, gives a chance for some of the charge carriers to spread out. Exposing the system to an external bistable potential, more intense at the two ends of the semiconductor layer, forces the outward-moving charge carriers to condense around two localised positions. As a result, charge carriers are dense in the central region and in two symmetrically positioned regions away from the centre. Using numerical simulation, in the framework of three-state approximation, we investigate the mobility of charge carriersas a function of different controlling parameters. In the presence of two time-varying signals, we calculate explicitly the transition rates from the middle layer towards the edges of the semiconductor layer and vice versa. We alsostudy the stochastic resonance by monitoring the asymmetric mean position of the charge carrier distribution, that is triggered by the synchronisation of signals with the noise-driven transition.

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