Spin-texture inversion in the giant Rashba semiconductor BiTeI

Semiconductors with strong spin-orbit interaction as the underlying mechanism for the generation of spin-polarized electrons are showing potential for applications in spintronic devices. Unveiling the full spin texture in momentum space for such materials and its relation to the microscopic structure of the electronic wave functions is experimentally challenging and yet essential for exploiting spin-orbit effects for spin manipulation. Here we employ a state-of-the-art photoelectron momentum microscope with a multichannel spin filter to directly image the spin texture of the layered polar semiconductor BiTeI within the full two-dimensional momentum plane. Our experimental results, supported by relativistic ab initio calculations, demonstrate that the valence and conduction band electrons in BiTeI have spin textures of opposite chirality and of pronounced orbital dependence beyond the standard Rashba model, the latter giving rise to strong optical selection-rule effects on the photoelectron spin polarization. These observations open avenues for spin-texture manipulation by atomic-layer and charge carrier control in polar semiconductors.This work was supported by DFG (through SFB 1170 'ToCoTronics') and through FOR1162 (P3). We acknowledge the support by the Basque Departamento de Educacion, UPV/EHU (Grant Number IT-756-13), Spanish Ministerio de Economia y Competitividad (MINECO Grant Number FIS2013-48286-C2-2-P), Tomsk State University Academic D.I. Mendeleev Fund Program in 2015 (Research Grant Number 8.1.05.2015), the Russian Foundation for Basic Research (Grant Numbers 15-02-01797 and 15-02-589 02717). Partial support by the Saint Petersburg State University (Grant Number 15.61.202.2015) is also acknowledged

Exact functionals and their core

exact functionals, exact cooperative games, coherent lower prevision, core,

Modelling tasks: insight into mathematical understanding

It is claimed, students’ communication of their solutions to modelling tasks gives insight into the depth of their mathematical understandings and how they use prior knowledge of the context of a task in their solution. In the example given, both students, Tabitha and Tanya, take an integrating approach to dealing with mathematics and reality in such tasks and their manner of dealing with the context of real world tasks remained stable from Year 9 to Year 11. In addition, communicative artefacts required by the tasks help reveal the students’ deepening understanding of mathematics

Enriching Wayfinding Instructions with Local Landmarks

Abstract. Navigation services communicate optimal routes to users by providing sequences of instructions for these routes. Each single instruction guides the wayfinder from one decision point to the next. The instructions are based on geometric data from the street network, which is typically the only dataset available. This paper addresses the question of enriching such wayfinding instructions with local landmarks. We propose measures to formally specify the landmark saliency of a feature. Values for these measures are subject to hypothesis tests in order to define and extract landmarks from datasets. The extracted landmarks are then integrated in the wayfinding instructions. A concrete example from the city of Vienna demonstrates the applicability and usefulness of the method.

Gray platelet syndrome can mimic autoimmune lymphoproliferative syndrome.

International audienc

Gray platelet syndrome can mimic autoimmune lymphoproliferative syndrome.

International audienc

Caminhos do Significado em Atividades de Modelagem Matemática: um olhar sobre os interpretantes

ResumoNeste artigo apresentamos resultados de uma pesquisa na qual investigamos evidências de atribuição de significado em atividades de modelagem matemática. A pesquisa está fundamentada nos pressupostos teóricos da modelagem matemática e na semiótica Peirceana com foco na teoria dos interpretantes. A busca por evidências relacionadas à atribuição de significado é permeada pela análise dos interpretantes produzidos por um grupo de alunos de um curso de Licenciatura em Matemática no decorrer de etapas associadas ao desenvolvimento de atividades de modelagem. Por meio de tais interpretantes inferimos sobre a atribuição de significado para o problema e para a Matemática durante o desenvolvimento da atividade de modelagem analisada, traçando caminhos do significado