Stabilization and current-induced motion of antiskyrmion in the presence of anisotropic Dzyaloshinskii-Moriya interaction

Topological defects in magnetism have attracted great attention due to fundamental research interests and potential novel spintronics applications. Rich examples of topological defects can be found in nanoscale non-uniform spin textures, such as monopoles, domain walls, vortices, and skyrmions. Recently, skyrmions stabilized by the Dzyaloshinskii-Moriya interaction have been studied extensively. However, the stabilization of antiskyrmions is less straightforward. Here, using numerical simulations we demonstrate that antiskyrmions can be a stable spin configuration in the presence of anisotropic Dzyaloshinskii-Moriya interaction. We find current-driven antiskyrmion motion that has a transverse component, namely antiskyrmion Hall effect. The antiskyrmion gyroconstant is opposite to that for skyrmion, which allows the current-driven propagation of coupled skyrmion-antiskyrmion pairs without apparent skyrmion Hall effect. The antiskyrmion Hall angle strongly depends on the current direction, and a zero antiskyrmion Hall angle can be achieved at a critic current direction. These results open up possibilities to tailor the spin topology in nanoscale magnetism, which may be useful in the emerging field of skyrmionics.Comment: 31 pages, 6 figures, to appear in Physical Review

Development of Fine-Grained Spatial Resolution for an Integrated Health Impacts Assessment Tool for the Sacramento Region

Understanding the public health impacts of transportation plans can inform decision making and project prioritization. Because each plan and regional context is different, there is a need for site-specific methods to assess the extent and distribution of health impacts of changes to a region’s transportation system. To fill this need, researchers have developed the Integrated Transport and Health Impact Model (ITHIM), which predicts the public health impacts of transportation and land use scenarios from expected changes in air quality, traffic safety, and physical activity. However, current transportation health impact assessment models (including ITHIM) operate at coarse geographic scales (e.g., region or county) to quantify health changes. This research builds on previous work using ITHIM to generate demographically explicit health outcomes to provide neighborhood-level estimates of public health changes predicted from transportation plan scenarios in Sacramento, California.We assess the impacts of regional transportation plan scenarios on public health via changes in traffic injury and physical activity. Zip-code level results are mapped using a customizable web interface. Illustrative results indicate that the adopted regional transportation plan will lead to improved health outcomes, largely driven by the benefits of increased physical activity. However, these estimates vary widely across the region, with some communities expected to experience adverse impacts and others obtaining higher levels of benefit. We note that some of the variation may be the result of modeling noise, and we identify promising avenues for improving the robustness of estimates at small spatial scales.Disaggregation is important from sustainability and equity perspectives to determine the locations where and populations for whom the physical activity benefits of non-motorized transportation are outweighed by increased exposure to the risk of air pollution and injury or death. Providing an accessible, web-based tool to illustrate the effects of transportation plans and in communities across a region has the potential to elevate health and equity considerations in transportation decision making. The methods developed in this study can be refined and improved and applied elsewhere by modifying the source code, which is publicly available.View the NCST Project Webpag

New Tool Evaluates Health and Equity Impacts of Sacramento’s Regional Transportation Plans

There is growing value in developing regional transportation plans that foster safer, healthier, and more environmentally sustainable communities. Greater rates of active travel (walking and biking) can lead to improved health outcomes due to increases in physical activity and air quality improvements, although they also increase risks of traffic injury. Analytical tools that evaluate the distribution of outcomes and the tradeoffs between transportation plan alternatives are needed to inform public debate and ensure that gains in some health outcomes are not being undermined by losses elsewhere. Additionally, there is a need to evaluate the impacts of transportation plans on different demographic groups to work toward more equitable outcomes.This policy brief summarizes findings from a project that created a tool to investigate the distribution of public health impacts resulting from the implementation of a regional transportation plan in the six-county Sacramento Area Council of Governments (SACOG) region.View the NCST Project Webpag

3D Instances as 1D Kernels

We introduce a 3D instance representation, termed instance kernels, where instances are represented by one-dimensional vectors that encode the semantic, positional, and shape information of 3D instances. We show that instance kernels enable easy mask inference by simply scanning kernels over the entire scenes, avoiding the heavy reliance on proposals or heuristic clustering algorithms in standard 3D instance segmentation pipelines. The idea of instance kernel is inspired by recent success of dynamic convolutions in 2D/3D instance segmentation. However, we find it non-trivial to represent 3D instances due to the disordered and unstructured nature of point cloud data, e.g., poor instance localization can significantly degrade instance representation. To remedy this, we construct a novel 3D instance encoding paradigm. First, potential instance centroids are localized as candidates. Then, a candidate merging scheme is devised to simultaneously aggregate duplicated candidates and collect context around the merged centroids to form the instance kernels. Once instance kernels are available, instance masks can be reconstructed via dynamic convolutions whose weights are conditioned on instance kernels. The whole pipeline is instantiated with a dynamic kernel network (DKNet). Results show that DKNet outperforms the state of the arts on both ScanNetV2 and S3DIS datasets with better instance localization. Code is available: https://github.com/W1zheng/DKNet.Comment: Appearing in ECCV, 202

Magnetic field-modulated exciton generation in organic semiconductors: an intermolecular quantum correlation effect

Magnetoelectroluminescence (MEL) of organic semiconductor has been experimentally tuned by adopting blended emitting layer consisting of both hole and electron transporting materials. A theoretical model considering intermolecular quantum correlation is proposed to demonstrate two fundamental issues: (1) two mechanisms, spin scattering and spin mixing, dominate the two different steps respectively in the process of the magnetic field modulated generation of exciton; (2) the hopping rate of carriers determines the intensity of MEL. Calculation successfully predicts the increase of singlet excitons in low field with little change of triplet exciton population.Comment: 16 pages, 4 figure

In-plane Hall effect in rutile oxide films induced by the Lorentz force

The conventional Hall effect is linearly proportional to the field component or magnetization component perpendicular to a film. Despite the increasing theoretical proposals on the Hall effect to the in-plane field or magnetization in various special systems induced by the Berry curvature, such an unconventional Hall effect has only been experimentally reported in Weyl semimetals and in a heterodimensional superlattice. Here, we report an unambiguous experimental observation of the in-plane Hall effect (IPHE) in centrosymmetric rutile RuO2 and IrO2 single-crystal films under an in-plane magnetic field. The measured Hall resistivity is found to be proportional to the component of the applied in-plane magnetic field along a particular crystal axis and to be independent of the current direction or temperature. Both the experimental observations and theoretical calculations confirm that the IPHE in rutile oxide films is induced by the Lorentz force. Our findings can be generalized to ferromagnetic materials for the discovery of in-plane anomalous Hall effects and quantum anomalous Hall effects. In addition to significantly expanding knowledge of the Hall effect, this work opens the door to explore new members in the Hall effect family