10 research outputs found
Symmetry and Control of Spin-Scattering Processes in Two-Dimensional Transition Metal Dichalcogenides
Transition metal dichalcogenides (TMDs) combine interesting optical and
spintronic properties in an atomically-thin material, where the light
polarization can be used to control the spin and valley degrees-of-freedom for
the development of novel opto-spintronic devices. These promising properties
emerge due to their large spin-orbit coupling in combination with their crystal
symmetries. Here, we provide simple symmetry arguments in a group-theory
approach to unveil the symmetry-allowed spin scattering mechanisms, and
indicate how one can use these concepts towards an external control of the spin
lifetime. We perform this analysis for both monolayer (inversion asymmetric)
and bilayer (inversion symmetric) crystals, indicating the different mechanisms
that play a role in these systems. We show that, in monolayer TMDs, electrons
and holes transform fundamentally differently -- leading to distinct
spin-scattering processes. We find that one of the electronic states in the
conduction band is partially protected by time-reversal symmetry, indicating a
longer spin lifetime for that state. In bilayer and bulk TMDs, a hidden
spin-polarization can exist within each layer despite the presence of global
inversion symmetry. We show that this feature enables control of the interlayer
spin-flipping scattering processes via an out-of-plane electric field,
providing a mechanism for electrical control of the spin lifetime.Comment: 9 pages, 3 figure
Intenções reprodutivas de mulheres que vivenciam regime de alta fecundidade em um grande centro urbano
Cenas da circulação: fragmentos de uma etnografia sobre homossexualidade, gênero, cor e mestiçagem em uma favela do Rio de Janeiro
Sustentabilidade Hidroambiental de nascentes na bacia hidrográfica do rio Gramame no estado da Paraíba, Brasil
Growing knowledge: an overview of Seed Plant diversity in Brazil
Abstract An updated inventory of Brazilian seed plants is presented and offers important insights into the country's biodiversity. This work started in 2010, with the publication of the Plants and Fungi Catalogue, and has been updated since by more than 430 specialists working online. Brazil is home to 32,086 native Angiosperms and 23 native Gymnosperms, showing an increase of 3% in its species richness in relation to 2010. The Amazon Rainforest is the richest Brazilian biome for Gymnosperms, while the Atlantic Rainforest is the richest one for Angiosperms. There was a considerable increment in the number of species and endemism rates for biomes, except for the Amazon that showed a decrease of 2.5% of recorded endemics. However, well over half of Brazillian seed plant species (57.4%) is endemic to this territory. The proportion of life-forms varies among different biomes: trees are more expressive in the Amazon and Atlantic Rainforest biomes while herbs predominate in the Pampa, and lianas are more expressive in the Amazon, Atlantic Rainforest, and Pantanal. This compilation serves not only to quantify Brazilian biodiversity, but also to highlight areas where there information is lacking and to provide a framework for the challenge faced in conserving Brazil's unique and diverse flora