Exciton-exciton interaction engineering in coupled GaN quantum dots

We present a fully three-dimensional study of the multiexciton optical response of vertically coupled GaN-based quantum dots via a direct-diagonalization approach. The proposed analysis is crucial in understanding the fundamental properties of few-particle/exciton interactions and, more important, may play an essential role in the design/optimization of semiconductor-based quantum information processing schemes. In particular, we focus on the interdot exciton-exciton coupling, key ingredient in recently proposed all-optical quantum processors. Our analysis demonstrates that there is a large window of realistic parameters for which both biexcitonic shift and oscillator strength are compatible with such implementation schemes.Comment: 3 two-column pages, 3 figure

Theory of spin Coulomb drag in spin-polarized transport

URL:http://link.aps.org/doi/10.1103/PhysRevB.62.4853 DOI:10.1103/PhysRevB.62.4853We introduce a distinctive feature of spin-polarized transport, the spin Coulomb drag: there is an intrinsic source of friction for spin currents due to the Coulomb interaction between spin “up” and spin “down” electrons. We calculate the associated “spin trans-resistivity” in a generalized random-phase approximation and show that, to the leading order in the interactions, it has no contribution from correlated impurity scattering. We show that, in an appropriate range of parameters, such resistivity is measurable, and we propose an experiment to measure it.This research was supported by NSF Grant No. DMR-9706788

Fermionic correlations as metric distances : a useful tool for materials science

We introduce a rigorous, physically appealing, and practical way to measure distances between exchange-only correlations of interacting many-electron systems, which works regardless of their size and inhomogeneity. We show that this distance captures fundamental physical features such as the periodicity of atomic elements, and that it can be used to effectively and efficiently analyze the performance of density functional approximations. We suggest that this metric can find useful applications in high-throughput materials design.Comment: 5 pages, 4 figure