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

High field and Coulomb interaction effects on spin injection in degenerate semiconductors

doi: 10.1088/0268-1242/19/4/126We analyse the combined effect of high electric field and Coulomb interaction on spin transport in semiconductors. We concentrate on the experimentally relevant regime characterized by T lap TF (intermediate to degenerate), where TF = εF/kB is the Fermi temperature. By the careful analysis of the downstream spin diffusion length Ld, we (i) demonstrate that in this regime carrier-carrier interactions become important and (ii) introduce the 'semiconductor degenerate' regime, in which spin-transport properties of a degenerate semiconductor are substantially modified by applying a modest electric field. Finally we discuss how the electric field and Coulomb interaction concur to influence the magnetoresistance of a trilayer system

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