SIMULATIONS OF FLUCTUATIONS IN QUANTUM-WIRE MESOSCOPIC SYSTEMS

We examine the geometry dependence of the conductance fluctuations in a quantum wire, using the recursive Green's function technique, by cha nging the width of a wire with fixed length. In the experimental situa tion, the quantum wire is 'connected' to 'wide' and 'long' disordered contact regions which are often ignored in calculations. This more com plicated quantum wire geometry lends itself to a numerical approach bu t would be very difficult to tackle from the viewpoint of the diagramm atic perturbation theory. We can include these disordered contact regi ons easily in our calculations: and our numerical results suggest that the presence of these contacts tends to reduce the fluctuations. This is a consequence of entering the transport 'localization regime', whe re the sample length is of the order of the localization length, for t he longer structure with the disordered contacts.