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In this report we study the quantum transport of charge carriers for low dimensional systems with spin-orbit coupling by means of Heisenberg's inequalities. To develop our analysis, an accurate \emph{gendanken} experiment was carefully put together, mainly based on the spin-field effect transistor phenomenology and taking into account several wide accepted approaches on quantum mechanical limited determinism. While verifying the applicability of time-energy uncertainty relation (TEUR) during electronic wavepacket's evolution through a semiconductor quantum wire, some qualitative information related the dynamic behavior of the system is found. The problem is also approached in the framework of the stationary phase method to guarantee robust coherence for wavepacket's evolution, which lately implies certain restrictions on the incident energy values for the envisioned cases. Tailoring different input parameters such as: incoming particles spin polarization, barrier thickness and Rashba's spin-orbit interaction (R-SOI) strength, we have observed appealing effects while the packet evolves through a quasi-1D heterostructure. Hopefully some of them could be of help in spintronics device designing. We have obtained most of the numerical simulation results, within the so-called conservation zone. However, for certain barrier thicknesses, some values drop into the forbidden area regarding the clear theoretical limit imposed by the TEUR. As an expected bonus throughout our theoretical validation of the TEUR, spin splitting due to finite values of R-SOI was nicely noticed., Comment: 6 pages, 8 figures

Multicomponent-multiband fluxes of spim-charge carriers, whose components propagate mixed and synchronously, with \emph{a priori} nonzero incoming amplitudes, do not obey the standard unitarity condition on the scattering matrix for an arbitrary basis set. For such cases, we have derived a robust theoretical procedure, which is fundamental in quantum-transport problems for unitarity preservation and we have named after \emph{structured unitarity condition}. Our approach deals with $(N \times N)$ interacting components (for $N \geq 2$), within the envelope function approximation (EFA), and yet the standard unitary properties of the ($N = 1$) scattering matrix are recovered. Rather arbitrary conditions to the basis-set and/or to the output scattering coefficients, are not longer required, if the \emph{eigen}-functions are orthonormalized in both the configuration and the spinorial spaces. We expect the present model to be workable, for different kind of multiband-multicomponent physical systems described by Hermitian Hamiltonians within the EFA, with small transformations if any. We foretell the interplay for the state-vector transfer matrix, together with the large values of its condition number, as a novel complementary tools for a more accurate definition of the threshold for tunnelling channels in a scattering experiment., Comment: 32 pages, 7 figures, 1 table

We studied the spin-dependent quantum transport properties using a simple modelling of a Datta-Das spin transistor. We refine previous results by accounting the propagation medium changes of opacity felt by itinerant electrons, when the gate-voltage is switched on and modelling them via the transversal energy levels mismatch. Monitoring the topological-dependent conductance, we are able to identify the device operating points. If the incoming electrons energy approaches the biased-induced barriers height, the spin-resolved conductance oscillations become significant. In a zero temperature picture, our computations of the spin-dependent conductance as function of the electric field at the region below the gate electrode suggest the feasibility of the modeled device. Although we demonstrate that phase time may not be spin-resolved, our simulation allows us to evaluate the time that takes an electron to experience a spin-flip process, resulting in an order of magnitude lower than typical values of the spin relaxation times., 7 pages, 7 figures

The evolution of transverse-momentum-dependent effective band offset ($V_{\mathrm{eff}}$) profile for heavy (\emph{hh})- and light-holes (\emph{lh}), is detailed studied. Several new features in the metamorphosis of the standardized fixed-height $V_{\mathrm{eff}}$ profile for holes, in the presence of gradually increasing valence-band mixing and pseudomorphic strain, are presented. In some $III-V$ unstrained semiconducting layered heterostructures a fixed-height potential, is not longer valid for \emph{lh}. Indeed, we found ---as predicted for electrons---, permutations of the $V_{\mathrm{eff}}$ character for \emph{lh}, that resemble a "\emph{keyboard}", together with bandgap changes, whenever the valence-band mixing varies from low to large intensity. Strain is able to diminish the \emph{keyboard} effect on $V_{\mathrm{eff}}$, and also makes it emerge or vanish occasionally. We found that multiband-mixing effects and stress induced events, are competitors mechanisms that can not be universally neglected by assuming a fixed-height rectangular spatial distribution for fixed-character potential energy, as a reliable test-run input for heterostructures. Prior to the present report, neither direct transport-domain measurements, nor theoretical calculations addressed to these $V_{\mathrm{eff}}$ evolutions and permutations, has been reported for holes, as far as we know. Our results may be of relevance for promising heterostructure's design guided by valence-band structure modeling to enhance the hole mobility in $III-V$ materials., 15 pages, 6 figures. arXiv admin note: text overlap with arXiv:1302.6985

A model is presented, consisting of a single structureless particle on the line subject to a potential with three minima, with an exactly soluble ground level. In this model the ground level probability density becomes more sensitive to the global shape of the potential as the distance between the minima increases, so that for big enough distances small variations in the potential bring a qualitative change in the probability density, taking it from a unimodal, localized, distribution, to a bimodal one. We conjecture that this effect, of which we have not found any precedent in the literature, may be relevant in the design and characterization of mesoscopic devices such as triple quantum well systems., 20 pages, 8 figures

We present the metamorphosis in the effective-potential profile of layered heterostructures, for several III-V semiconductor binary compounds, when the band mixing of light and heavy holes increases. A root-locus-like procedure, is directly applied to an eigenvalue quadratic problem obtained from a multichannel system of coupled modes, in the context of multiband effective mass approximation. By letting grow valence-band mixing, it is shown the standard fixed-height rectangular potential-energy for the scatterer distribution, to be a reliable test-run input for heavy holes. On the contrary, this scheme is no longer valid for light holes and a mutable effective \emph{band offset} profile has to be considered instead, whenever the in-plane kinetic energy changes., Comment: 12 pages, 5 figures

We study the time reversal and space inversion symmetry properties of those transfer matrices mostly used in the calculation of energy spectra and transport-process. We study the time reversal and space inversion symmetry properties of those transfer matrices mostly used in the calculation of energy spectra and transport-process quantities. We determine the unitary transformation relating transfer matrices. We consider the Kohn-Luttinger model for a quasi-2D system and show that even though the system studied in the (4 x 4) scheme satisfies all the symmetry requirements, the (2 x 2)subspaces do not fulfill such constrains, except in the Gamma point of the Brillouin Zone. We find new exchange properties between the (2\times 2)subspace quantities., 12 pages, none figures

An appropriate combination of the scattering theory and the transfer matrix formalism, for the solution of a (4 x 4) Kohn-Luttinger model, allow us to study the multichannel-multiband transmission process of heavy and light holes through a (GaAs/AlAs) superlattice. Appealing effects and interesting channel coupling phenomena, mediated by quasi-bond states, are clearly foreseen., 4 pages, 4 figures,Reduced version of a talk presented at the Iberoamerican Meeting on Nanostructures (Madrid, March 2003)