QUANTUM INTERFERENCE EFFECTS IN A PI-SHAPED ELECTRON WAVE-GUIDE

Ballistic electron transport in a PI-shaped quantum wire is investigat ed. The device conductance and bound-state energies are calculated on the basis of the tight-binding formalism. It is shown that the transmi ssion coefficient as a function of the distance between the source and drain wires of the PI structure d is represented by a quasi-periodic sequence of unity transmission separated by valleys of nearly zero tra nsmission. This is the case in the energy region of the stop-band beha viour of a right-angle-bend waveguide of the same width w. The bound-s tate spectrum of the PI and double-bend structures is studied in the e ntire region of variations of the parameter alpha = d/w. In the double bend, the lowest bound-state energy DELTAE(b) is shown to be a non-mo notonic function of alpha, which is zero at alpha = -1 (the limiting c ase of a straight wire), reaches its maximum DELTAE(b)max almost-equal -to 0.15 (in units of the energy of the propagation threshold E(th)) a t alpha almost-equal-to -0.3, and then tends to the asymptotic value a lmost-equal-to 0.07, which corresponds to the bound-state energy in a right-angle-bend waveguide. Special emphasis is paid to the possibilit y of experimental identification of quantum interference effects.