Physics Candidate Presentation-March 28, 2012

Spintronics Research

Abstract: Spintronics is an emerging field in which the quantum mechanical spin of the electron is used for switching purposes and to communicate information. Spin-dependent effects arise from interactions of the electron with an external magnetic field via the Zeeman effect or with magnetic properties of the conduction material. Aharonov-Bohm (AB) rings with embedded quantum dots (QD’s) are examples of nano-scale devices which have shown the potential for spin-dependent transport. When electron spin-degeneracy is lifted, the transmission resonant modes through the QD’s provide powerful methods for producing spin-polarization filters which have important potential applications in spintronic device technologies. Sharpened AB oscillations for parallel double QD’s in resonance provide a feasible mechanism for spin polarization or filtering of spin states with a small value of external field, as identified by calculating the differential weighted spin-polarization. When the transmission resonance is a sharp function of energy or magnetic field, opposite electron spin states are shown in our models to be transmitted with a high degree of polarization. It is also shown that the combination of AB and Zeeman effects produce novel transmission phenomenon such as non-periodic AB oscillations, QD-coupling-dependent dominance of either effect, and the transition from transmission resonance crossings into anti-crossings. In addition, the shift of the QD energy levels due to Zeeman splitting disrupts the normal periodic modulation of the transmission seen with a pure AB-effect, even producing Fano-type resonances as a function of magnetic flux. Research also demonstrates enhanced spin polarization effects within a double AB-ring structure (two rings in series). The number of transmission resonances doubles for this structure, resulting in unique spins polarization features as a function of electron energy and Zeeman splitting.

by
Eric Hedin
Assistant Professor
Ball State University

Wednesday, March 28, 2012
4:00 PM
CP 144