Manipulating Single Spins in Quantum Dots Coupled to Ferromagnetic Leads

TL;DR

This paper explores how to generate, manipulate, and measure single spins in quantum dots connected to ferromagnetic leads, highlighting the control via magnetic fields, exchange interactions, and electrical voltages.

Contribution

It introduces methods to control quantum-dot spin polarization using magnetic properties, exchange fields, and voltages, advancing spin manipulation techniques in quantum dot systems.

Findings

Spin polarization depends on lead magnetization and coupling.

Exchange field can be tuned by gate and bias voltages.

Transport properties reflect the quantum-dot spin state.

Abstract

We discuss the possibility to generate, manipulate, and probe single spins in single-level quantum dots coupled to ferromagnetic leads. The spin-polarized currents flowing between dot and leads lead to a non-equilibrium spin accumulation, i.e., a finite polarization of the dot spin. Both the magnitude and the direction of the dot's spin polarization depends on the magnetic properties of leads and their coupling to the dot. They can be, furthermore, manipulated by either an externally applied magnetic field or an intrinsically present exchange field that arises due to the tunnel coupling of the strongly-interacting quantum-dot states to spin-polarized leads. The exchange field can be tuned by both the gate and bias voltage, which, therefore, provide convenient handles to manipulate the quantum-dot spin. Since the transmission through the quantum-dot spin valve sensitively depends on the state of the quantum-dot spin, all the dynamics of the latter is reflected in the transport properties of the device.