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

Ballistic electron transport in a PI-shaped quantum wire is investigated. The device conductance and bound-state energies are calculated on the basis of the tight-binding formalism. It is shown that the transmission 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 transmission. This is the case in the energy region of the stop-band behaviour of a right-angle-bend waveguide of the same width w. The bound-state spectrum of the PI and double-bend structures is studied in the entire 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-monotonic function of alpha, which is zero at alpha = -1 (the limiting case 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)) at alpha almost-equal-to -0.3, and then tends to the asymptotic value almost-equal-to 0.07, which corresponds to the bound-state energy in a right-angle-bend waveguide. Special emphasis is paid to the possibility of experimental identification of quantum interference effects.