5,128 research outputs found
Controlling Decoherence of Transported Quantum Spin Information in Semiconductor Spintronics
We investigate quantum coherence of electron spin transported through a
semiconductor spintronic device, where spins are envisaged to be controlled by
electrical means via spin-orbit interactions. To quantify the degree of spin
coherence, which can be diminished by an intrinsic mechanism where spin and
orbital degrees of freedom become entangled in the course of transport
involving spin-orbit interaction and scattering, we study the decay of the
off-diagonal elements of the spin density matrix extracted directly from the
Landauer transmission matrix of quantum transport. This technique is applied to
understand how to preserve quantum interference effects of fragile
superpositions of spin states in ballistic and non-ballistic multichannel
semiconductor spintronic devices.Comment: 7 pages, 3 color EPS figures, prepared for Proceedings of
International Symposium on Mesoscopic Superconductivity and Spintronics 2004
(Atsugi, Japan, March 1-4, 2004
Classical and Non-Relativistic Limits of a Lorentz-Invariant Bohmian Model for a System of Spinless Particles
A completely Lorentz-invariant Bohmian model has been proposed recently for
the case of a system of non-interacting spinless particles, obeying
Klein-Gordon equations. It is based on a multi-temporal formalism and on the
idea of treating the squared norm of the wave function as a space-time
probability density. The particle's configurations evolve in space-time in
terms of a parameter {\sigma}, with dimensions of time. In this work this model
is further analyzed and extended to the case of an interaction with an external
electromagnetic field. The physical meaning of {\sigma} is explored. Two
special situations are studied in depth: (1) the classical limit, where the
Einsteinian Mechanics of Special Relativity is recovered and the parameter
{\sigma} is shown to tend to the particle's proper time; and (2) the
non-relativistic limit, where it is obtained a model very similar to the usual
non-relativistic Bohmian Mechanics but with the time of the frame of reference
replaced by {\sigma} as the dynamical temporal parameter
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