INVESTIGATION OF THE QUANTUM CONDUCTANCE CHARACTERISTICS OF SOME MESOSCOPIC DEVICES

Abstract

In the present thesis the quantum transport characteristics of mesoscopic system under the effect of magnetic field and in the Coulomb blockade regime are studied. Such mesoscopic system is modeled as two semiconductor quantum dots coupled to superconducting leads via two quantum point contacts.

The conductance of such mesoscopic junction has been obtained in terms of the Andreev reflection tunneling probability by using the Landauer-Biittiker equation. This Andreev reflection tunneling probability was deduced by solving the Bogoliubov-deGennes (BdG) equation, describing the electron transport through the junction. Numerical calculation has been performed, treating the electron transport as a stochastic process.

The obtained results show that the electron transport through such mesoscopic device has a coherent property, so as the devices size is less than the mean free path of electrons and the corresponding coherence length of Cooper pair. An important result was obtained which shows the deviation of the periodic oscillation of the dependence of the conductance on the magnetic field from the conventional quantum flux. However, it should be modified by a parameter, which is very sensitive to the quantum dot size. The periodic oscillation of the conductance with the