Generation of spin-polarized current using multi-terminated quantum dot with spin-orbit interaction

TL;DR

This paper theoretically investigates how multi-terminated quantum dots with spin-orbit interaction can generate spin-polarized currents, revealing conditions for polarization enhancement and effects of magnetic fields.

Contribution

It introduces a minimal two-level quantum dot model connected to multiple leads to analyze spin-polarized current generation without magnetic fields.

Findings

Spin-polarized current can be generated with at least three leads.

Resonant tunneling significantly enhances polarization.

Weak magnetic fields induce polarization even in two-terminal setups.

Abstract

We theoretically examine generation of spin-polarized current using multi-terminated quantum dot with spin-orbit interaction. First, a two-level quantum dot is analyzed as a minimal model, which is connected to $N$ ($\ge 2$) external leads via tunnel barriers. When an unpolarized current is injected to the quantum dot from a lead, a polarized current is ejected to others, similarly to the spin Hall effect. In the absence of magnetic field, the generation of spin-polarized current requires $N \ge 3$. The polarization is markedly enhanced by resonant tunneling when the level spacing in the quantum dot is smaller than the level broadening due to the tunnel coupling to the leads. In a weak magnetic field, the orbital magnetization creates a spin-polarized current even in the two-terminal geometry (N=2). The numerical study for generalized situations confirms our analytical result using the two-level model.