Spin transmission control in helical magnetic fields

We calculate spin transport in two-dimensional waveguides in the presence of spatially modulated Zeeman-split energy bands. We show that in a regime where the spin evolution is predominantly adiabatic the spin backscattering rate can be tuned via diabatic Landau-Zener transitions between the spin-split bands [C. Betthausen et. al., Science 337, 324 (2012)]. This mechanism is tolerant against spin-independent scattering processes. Completely spin-polarized systems show full spin backscattering, and thus current switching. In partially spin-polarized systems a spatial sequence of Landau-Zener transition points enhances the resistance modulation via reoccupation of backscattered spin-polarized transport modes. We discuss a possible application as a spin transistor.Comment: Theory related to the adiabatic spin transistor concept (C. Betthausen et al., Science 337, 324 (2012), DOI: 10.1126/science.1221350

Signatures of spin-preserving symmetries in two-dimensional hole gases

We investigate ramifications of the persistent spin helix symmetry in two-dimensional hole gases in the conductance of disordered mesoscopic systems. To this end we extend previous models by going beyond the axial approximation for III-V semiconductors. For heavy-hole subbands we identify an exact spin-preserving symmetry analogous to the electronic case by analyzing the crossover from weak antilocalization to weak localization and spin transmission as a function of extrinsic spin-orbit interaction strength.Comment: 7 pages, 3 figures; reference adde

Schwerpunkt: Rechtsextremismus und Soziale Arbeit

Das SI:SO-Heft widmet sich den folgenden Fragen: - Unter welchen Gesichtspunkten lassen sich Rechtspopulismus und Rechtsextremismus differenziert diskutieren? - Wie werden Rechtsextreme bestimmt und Rechtsextremismus identifiziert? - Inwiefern ist Soziale Arbeit von Rechtsextremismus und Rechtspopulismus betroffen? - Welche Kritiken gelten als zulässig, welche nicht und welche Auseinandersetzungen werden in der Sozialen Arbeit gemieden? - Welche politischen und zivilgesellschaftlichen Beiträge leistet Soziale Arbeit im Phänomenbereich Rechtsextremismus und Rechtspopulismus? - Welche Folgen ergeben sich für Hochschulen und Studium im Umgang mit Rechtsextremismus und Rechtspopulismus

The neutron and its role in cosmology and particle physics

Experiments with cold and ultracold neutrons have reached a level of precision such that problems far beyond the scale of the present Standard Model of particle physics become accessible to experimental investigation. Due to the close links between particle physics and cosmology, these studies also permit a deep look into the very first instances of our universe. First addressed in this article, both in theory and experiment, is the problem of baryogenesis ... The question how baryogenesis could have happened is open to experimental tests, and it turns out that this problem can be curbed by the very stringent limits on an electric dipole moment of the neutron, a quantity that also has deep implications for particle physics. Then we discuss the recent spectacular observation of neutron quantization in the earth's gravitational field and of resonance transitions between such gravitational energy states. These measurements, together with new evaluations of neutron scattering data, set new constraints on deviations from Newton's gravitational law at the picometer scale. Such deviations are predicted in modern theories with extra-dimensions that propose unification of the Planck scale with the scale of the Standard Model ... Another main topic is the weak-interaction parameters in various fields of physics and astrophysics that must all be derived from measured neutron decay data. Up to now, about 10 different neutron decay observables have been measured, much more than needed in the electroweak Standard Model. This allows various precise tests for new physics beyond the Standard Model, competing with or surpassing similar tests at high-energy. The review ends with a discussion of neutron and nuclear data required in the synthesis of the elements during the "first three minutes" and later on in stellar nucleosynthesis.Comment: 91 pages, 30 figures, accepted by Reviews of Modern Physic

Numerical Data from the Dissertation "Spin Transport in Two-Dimensional Electron and Hole Gases"

Numerical Data underlying the figures used in the Dissertation "Spin Transport in Two-Dimensional Electron and Hole Gases" by Tobias Dollinge

Spin transport in two-dimensional electron and hole gases

This dissertation focuses on spin based phenomena of transport in low-dimensional mesoscopic systems. The work contains the theoretical discussion of an experimentally verified spin-transistor concept, which is based on controlling adiabaticity of spin evolution in dilute magnetic semiconductors. Furthermore the effect of spin dephasing on the weak localization and the weak antilocalization conductance corrections is investigated. In this context, the influence of spin-orbit interaction that scales cubically with the momentum on n- and p-type charge transport is examined. The analyses presented here are based on numerical transport simulations and semiclassical frameworks

Latex Archiv zur Dissertation "Spin Transport in Two-Dimensional Electron- and Hole Gases" von Tobias Dollinger

Bilder und Latex-Quelltext zur Dissertatio

Signatures of spin-preserving symmetries in two-dimensional hole gases

We investigate ramifications of the persistent spin helix symmetry in two-dimensional hole gases in the conductance of disordered mesoscopic systems. To this end we extend previous models by going beyond the axial approximation for III-V semiconductors. We identify for heavy-hole subbands an exact spin-preserving symmetry analogous to the electronic case by analyzing the crossover from weak anti-localization to weak localization and spin transmission as a function of extrinsic spin-orbit interaction strength