Dept. of Physics, SUNY–Buffalo, Buffulo, NY 14260, U.S.A.
Institute for Theoretical PhysicsUniversity of Regensburg, 93040 Regensburg, Germany
The anticipated limits of scaling for silicon CMOS transistors have spurred researchers to explore more exotic schemes for computation. A promising approach comes from the field of spin electronics or spintronics,1,2 which seeks to manipulate and use the spin of carriers and not just their charge. An impressive success of spintronic applications has been achieved in metal-based structures that utilize magnetoresistive effects for substantial improvements in the performance of computer hard drives and magnetic random access memories (MRAMs).3,4 Correspondingly, the theoretical understanding of spin transport is usually limited to the metallic regime in linear response, which, while providing a good description for data storage and magnetic memory devices, is not sufficient for signal processing and digital logic. In contrast, much less is known about possible applications of semiconductor spintronics and spin transport in related structures that could utilize strong intrinsic nonlinearities in current-voltage characteristics to implement spin-based logic. Spin transport differs from charge transport in that spin orientation, even in the absence of magnetic impurities, is a nonconserved quantity due to spin-orbit and hyperfme coupling.1
Many basic questions, such ...