Van der Waals spin valves

We propose spin valves where a 2D non-magnetic conductor is intercalated between two ferromagnetic insulating layers. In this setup, the relative orientation of the magnetizations of the insulating layers can have a strong impact on the in-plane conductivity of the 2D conductor. We first show this for a graphene bilayer, described with a tight-binding model, placed between two ferromagnetic insulators. In the anti-parallel configuration, a band gap opens at the Dirac point, whereas in the parallel configuration, the graphene bilayer remains conducting. We then compute the electronic structure of graphene bilayer placed between two monolayers of the ferromagnetic insulator CrI$_3$, using density functional theory. Consistent with the model, we find that a gap opens at the Dirac point only in the antiparallel configuration.Comment: 5 pages, 4 figure

Uma perspectiva multidimensional na formação de professores para o ensino da fisica moderna e contemporanea

É exigido que a educação em ciência hoje questione as relações entre ciência, tecnologia, sociedade e o mundo. No contexto da formação de professores de Física, esta investigação insere-se num quadro de valorização do conhecimento e da reflexão epistemológica e ontológica, com vista a construções identitárias, transformadoras e para a intervenção. É descrito um percurso de formação centrando o tema da Física Quântica e a complexidade enquanto quadro de referência. Os resultados mostram o despertar de uma consciência, potenciadora de prática lectiva, da ciência como face da cultura, que se integra no ritmo do tempo e que estabelece com a nossa vida uma estreita relação. A multidimensionalidade emerge como estruturante de um modelo de formação para o mundo em mudança, onde os processos reflexivos e identitários se constituem essenciais

Solitons with Cubic and Quintic Nonlinearities Modulated in Space and Time

This work deals with soliton solutions of the nonlinear Schroedinger equation with cubic and quintic nonlinearities. We extend the procedure put forward in a recent Letter and we solve the equation in the presence of linear background, and cubic and quintic interactions which are modulated in space and time. As a result, we show how a simple parameter can be used to generate brightlike or darklike localized nonlinear waves which oscillate in several distinct ways, driven by the space and time dependence of the parameters that control the trapping potential, and the cubic and quintic nonlinearities.Comment: 4 pages, 6 figures; version to appear in PRE, R

Entropy function for rotating extremal black holes in very special geometry

We use the relation between extremal black hole solutions in five- and in four-dimensional N=2 supergravity theories with cubic prepotentials to define the entropy function for extremal black holes with one angular momentum in five dimensions. We construct two types of solutions to the associated attractor equations.Comment: 15 pages, minor change