Controlling spin polarization of a quantum dot via a helical edge state

TL;DR

This paper demonstrates how a helical edge state can be used to control the spin polarization of a quantum dot, revealing bias-dependent magnetization and conductance features that depend on the relative axes.

Contribution

It introduces a theoretical framework for manipulating quantum dot spin states via helical edge states using a generalized master equation approach.

Findings

Bias voltage controls quantum dot magnetization direction.

Backscattering conductance shows a resonance at Zeeman energy.

Bias asymmetry reveals the HLL spin quantization axis.

Abstract

We investigate a Zeeman-split quantum dot (QD) containing a single spin 1/2 weakly coupled to a helical Luttinger liquid (HLL) within a generalized master equation approach. The HLL induces a tunable magnetization direction on the QD controlled by an applied bias voltage when the quantization axes of the QD and the HLL are noncollinear. The backscattering conductance (BSC) in the HLL is finite and shows a resonance feature when the bias voltage equals the Zeeman energy in magnitude. The observed BSC asymmetry in bias voltage directly reflects the quantization axis of the HLL spin.