Multisublevel magnetoquantum conductance in single and coupled double quantum wires - art. no. 115320

We study the ballistic and diffusive magnetoquantum transport using a typic al quantum point contact geometry for single and tunnel-coupled double wire s that are wide (less than or similar to1 mum) in one perpendicular directi on with densely populated sublevels and extremely confined in the other per pendicular (i.e., growth) direction. A general analytic solution to the Bol tzmann equation is presented for multisublevel elastic scattering at low te mperatures. The solution is employed to study interesting magnetic-field de pendent behavior of the conductance such as a large enhancement and quantum oscillations of the conductance for various structures and field orientati ons. These phenomena originate from the following field-induced properties: magnetic confinement, displacement of the initial- and final-state wave fu nctions for scattering, variation of the Fermi velocities, mass enhancement , depopulation of the sublevels and anticrossing (in double quantum wires). The magnetoconductance is strikingly different in long diffusive (or rough . dirty) wires from the quantized conductance in short ballistic (or clean) wires. Numerical results obtained for the rectangular confinement potentia ls in the growth direction are satisfactorily interpreted in terms of the a nalytic solutions based on harmonic confinement potentials. Some of the pre dicted features of the field-dependent diffusive and quantized conductances are consistent with recent data from GaAs/AlxGa1-xAs double quantum wires.