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

TL;DR

This paper explores quantum transport in ladder-type networks, revealing how topology, nonlinearity, and spin-orbit interactions influence transmission, switching effects, and spin filtering in mesoscopic quantum dot systems.

Contribution

It provides new insights into the effects of network topology, defects, and spin-orbit interactions on quantum transport and spin filtering in ladder networks.

Findings

Transition from anti-phase to degenerate spectra at critical energy

Spin filtering occurs with spin-orbit interaction

Defects induce switching effects in transmission

Abstract

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 $\epsilon<\epsilon_c$. In the presence of the electric-field induced spin-orbit interaction (SOI), an obvious spin filtering occurs against the spin-unpolarized injection. Against the spin-polarized injection, on the other hand, the spin transport shows spin-flip (magnetization reversal) oscillations with respect to SOI. We also show a role of soliton in the context of its transport through the ladder networks.