ABSTRACT

Spintronics is an emerging field in which the quantum mechanical

spin of the electron is used for switching purposes and to communicate information [1]. Spin-dependent effects arise from

interactions of the electron with an external magnetic field or with

magnetic properties of the conduction material. Future spintronic

devices hold the promise of faster switching speeds, less electric

power consumption, and higher density of circuit elements [2].

Aharonov-Bohm (AB) rings are examples of nanoscale devices

which have shown the potential for spin-dependent transport

[3, 4]. An important feature of an AB interferometer with a

quantum dot (QD) embedded in one or both arms is the ability

to probe the total spin of the electronic state of the QD. When

electron spin-degeneracy is lifted, the transmission resonant modes

through the QDs indicate powerful methods for producing spin-

polarization filters which have important potential applications in

spintronic device technologies. Investigating electron-spin transport

in semiconductor nanostructures and nanoscale electronic devices

including QDs has attracted much attention [5-8]. QDs with spin-

split energy levels embedded in AB rings offer unique possibilities

for manipulating and utilizing the spin of electrons in individual

quantum states [9]. The main topics of research have focused on

studying the fundamental aspects of the spin-dependent transport

(e.g., spin coherence times, many-body effects such as the Kondo

effect or spin-charge separation [10, 11], and spin-dependent

tunneling [12]) and to developing and optimizing semiconductor

spintronics device applications, such as spin transistors and spin

qubits [5]. More recently, both experimental and theoretical studies

have shown the possibility of preparing and manipulating spin-

polarized electron states in graphene [13, 14].