الفهرس 
Chapter one: introductionOnly 14 pages are availabe for public view
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Abstract
In this thesis the Quantum transport characteristics of mesoscopic systems under the effect of Coulomb blockade and magnetic field are studied. We shall consider three different models as : (i) A semiconductor quantum dot is coupled to a superconducting leads via a quantum point contact (Fig.II.l). (ii) A quantum dot is coupled via tunnel barriers to two superconducting electron reservoirs. The quantum dot is made of semiconductor heterostructure (Fig.II.2). (iii) An electronic stub tuner modeled as S-Sm-S-Sm-S ( S-superconductor, Sm-semiconductor) (Fig.II.3).
The Josephson current has been obtained in terms of the Andreev reflection amplitude. This Andreev reflection amplitude was deduced by Solving the Bogoliubov-de Gennes (BdG) equation, describing the electron transport through the junction. Numerical calculation of the Josephson current has been performed for different values of the phase angle, temperatures, the magnetic field and the distance between the Superconducting leads.
The obtained results, for the first model, show that the electron transport through the device has a coherent property. An important result was obtained for the variation of the magnetic length with the applied magnetic field. This result shows that the correlated electrons affected by an interplay between the magnetic length and the size of the present device. The current dependence on the dimensions of the device shows an oscillatory behavior for multiple interacting channels, while for a single channel, this dependence is a decreasing function. These results are explained according to the clean limit theory of the mesoscopic system and found concordant with those in the literature. Also, for the second model, it is found that the current-phase angle (I-φ) of Cooper pairs relation exhibits a peak at φ≈ 0.50 at low temperature. However, this peak shifts to a lower values as the temperature increases. Also, this relation (I-φ) does not change as the magnetic field varies. The relation ( I-B ) ( B- magnetic field ) has the same peak position for different values of (φ) and temperatures. These results are explained according to the resonant tunneling regime of electrons through such junction and show a qualitative agreement with those results available in the literature.
Now, for the third model, the dependence of the current density on phase angle shows a periodic variation. While the oscillation features of the current density with the magnetic field are predicted to be due to quantum interference of electron waves. This behavior is noticed by other authors for such a quantum interference tuner.
Such investigations on mesoscopic systems in this thesis might be valuable for nanotechnology of nanoelectronic devices.
The thesis contains four chapters. The first one reviewed the historical works on the mesoscopic systems. The second chapter treats the theory of the considered mesoscopic junction. The numerical calculations and results is given in chapter three and chapter four summarizes the main conclusions and appendix.