QUANTUM WAVE-GUIDE TRANSPORT WITH SIDE-BRANCH STRUCTURES - A RECURSIVE ALGORITHM

Electronic conductance of a quantum waveguide with side-branch structu res is investigated. We introduce impedance factors for geometric and potential scatterers and develop a recursive algorithm. impedance fact ors for several basic unit structures, recursion formulas, and an addi tion rule are presented with the use of one-dimensional quantum wavegu ide theory. The impedance factor of a complicated side-branch structur e can be evaluated from impedance factors of the individual parts cont ained in the structure as in the classical resistance-network calculat ion. This method makes conductance calculations simple since the wave functions of the structures are not required. With this method conduct ance properties of the quantum waveguides with different periodic side -branch structures (vertical structures) are studied in detail. Electr onic conductance of these side-branch modulators manifests band struct ure with fast oscillating regions and inherent regions. As the number of repeat structures increases, the number of sharp peaks in the oscil lating bands increases proportionally while the conductance profiles i n the inherent bands remain unchanged. Comparison with the conductance of similar periodic structures along the main wire (horizontal struct ures) reveals that the oscillating bands and inherent bands of the ver tical structure correspond to the transmission bands and forbidden ban ds of the horizontal structure, respectively.