8,197 research outputs found
Switchable valley functionalities of an junction in 2D semiconductors
We show that an junction in 2D semiconductors can flexibly
realize two basic valleytronic functions, i.e. valley filter and valley source,
with gate controlled switchability between the two. Upon carrier flux passing
through the junction, the valley filter and valley source functions are enabled
respectively by intra- and inter-valley scatterings, and the two functions
dominate respectively at small and large band-offset between the and
regions. It can be generally shown that, the valley filter effect has
an angular dependent polarity and vanishes under angular integration, by the
same constraint from time-reversal symmetry that leads to its absence in
one-dimension. These findings are demonstrated for monolayer transition metal
dichalcogenides and graphene using tight-binding calculations. We further show
that junction along chiral directions can concentrate the valley pump in an
angular interval largely separated from the bias direction, allowing efficient
havest of valley polarization in a cross-bar device
Leading Effect of CP Violation with Four Generations
In the Standard Model with a fourth generation of quarks, we study the
relation between the Jarlskog invariants and the triangle areas in the 4-by-4
CKM matrix. To identify the leading effects that may probe the CP violation in
processes involving quarks, we invoke small mass and small angle expansions,
and show that these leading effects are enhanced considerably compared to the
three generation case by the large masses of fourth generation quarks. We
discuss the leading effect in several cases, in particular the possibility of
large CP violation in processes, which echoes the heightened recent
interest because of experimental hints.Comment: 12 pages, no figur
ES2Net: An Efficient Spectral-Spatial Network for Hyperspectral Image Change Detection
Hyperspectral image change detection (HSI-CD) aims to identify the
differences in bitemporal HSIs. To mitigate spectral redundancy and improve the
discriminativeness of changing features, some methods introduced band selection
technology to select bands conducive for CD. However, these methods are limited
by the inability to end-to-end training with the deep learning-based feature
extractor and lack considering the complex nonlinear relationship among bands.
In this paper, we propose an end-to-end efficient spectral-spatial change
detection network (ES2Net) to address these issues. Specifically, we devised a
learnable band selection module to automatically select bands conducive to CD.
It can be jointly optimized with a feature extraction network and capture the
complex nonlinear relationships among bands. Moreover, considering the large
spatial feature distribution differences among different bands, we design the
cluster-wise spatial attention mechanism that assigns a spatial attention
factor to each individual band to individually improve the feature
discriminativeness for each band. Experiments on three widely used HSI-CD
datasets demonstrate the effectiveness and superiority of this method compared
with other state-of-the-art methods
- β¦