Quantum Transport in Ladder-Type Networks: Role of nonlinearity, topology and spin

We investigate quantum transport of electrons, phase solitons, etc. through mesoscopic networks of zero-dimensional quantum dots. Straight and circular ladders are chosen as networks with each coupled with three semi-infinite leads (with one incoming and the other two outgoing). Two transmission probabilities (TPs) as a function of the incident energy \(\epsilon\) show a transition from anti-phase aperiodic to degenerate periodic spectra at the critical energy \(\epsilon_c\) which is determined by a bifurcation point of the bulk energy dispersions. TPs of the circular ladder depend only on the parity of the winding number. Introduction of a single missing bond (MB) or missing step doubles the period of the periodic spectra at \(\epsilon>\epsilon_c\) . Shift of the MB by lattice constant results in a striking switching effect at \(\epsilon