Spin-current modulation and square-wave transmission through periodically stubbed electron waveguides

TL;DR

This paper investigates how periodically stubbed electron waveguides can control spin transport, achieving nearly perfect on/off transmission states and potential applications in spin transistors, with considerations of temperature effects.

Contribution

It introduces a method to modulate spin current using stub parameters in waveguides, demonstrating nearly square-wave transmission and potential for spin transistor design.

Findings

Complete spin blocking with specific waveguide and stub parameters

Square-wave transmission behavior with high on/off contrast

Modulation of spin current via defect insertion in stub superlattices

Abstract

Ballistic spin transport through waveguides, with symmetric or asymmetric double stubs attached to them periodically, is studied systematically in the presence of a weak spin-orbit coupling that makes the electrons precess. By an appropriate choice of the waveguide length and of the stub parameters injected spin-polarized electrons can be blocked completely and the transmission shows a periodic and nearly square-type behavior, with values 1 and 0, with wide gaps when only one mode is allowed to propagate in the waveguide. A similar behavior is possible for a certain range of the stub parameters even when two-modes can propagate in the waveguide and the conductance is doubled. Such a structure is a good candidate for establishing a realistic spin transistor. A further modulation of the spin current can be achieved by inserting defects in a finite-number stub superlattice. Finite-temperature effects on the spin conductance are also considered.