233 research outputs found
Intervalley coupling by quantum dot confinement potentials in monolayer transition metal dichalcogenides
Monolayer transition metal dichalcogenides (TMDs) offer new opportunities for
realizing quantum dots (QDs) in the ultimate two-dimensional (2D) limit. Given
the rich control possibilities of electron valley pseudospin discovered in the
monolayers, this quantum degree of freedom can be a promising carrier of
information for potential quantum spintronics exploiting single electrons in
TMD QDs. An outstanding issue is to identify the degree of valley
hybridization, due to the QD confinement, which may significantly change the
valley physics in QDs from its form in the 2D bulk. Here we perform a
systematic study of the intervalley coupling by QD confinement potentials on
extended TMD monolayers. We find that the intervalley coupling in such geometry
is generically weak due to the vanishing amplitude of the electron wavefunction
at the QD boundary, and hence valley hybridization shall be well quenched by
the much stronger spin-valley coupling in monolayer TMDs and the QDs can well
inherit the valley physics of the 2D bulk. We also discover sensitive
dependence of intervalley coupling strength on the central position and the
lateral length scales of the confinement potentials, which may possibly allow
tuning of intervalley coupling by external controlsComment: 17 pages, 14 figure
Scattering universality classes of side jump in anomalous Hall effect
The anomalous Hall conductivity has an important extrinsic contribution known
as side jump contribution, which is independent of both scattering strength and
disorder density. Nevertheless, we discover that side jump has strong
dependence on the spin structure of the scattering potential. We propose three
universality classes of scattering for the side jump contribution, having the
characters of being spin-independent, spin-conserving and spin-flip
respectively. For each individual class, the side jump contribution takes a
different unique value. When two or more classes of scattering are present, the
value of side jump is no longer fixed but varies as a function of their
relative disorder strength. As system control parameter such as temperature
changes, due to the competition between different classes of disorder
scattering, the side jump Hall conductivity could flow from one class dominated
limit to another class dominated limit. Our result indicates that magnon
scattering plays a role distinct from normal impurity scattering and phonon
scattering in the anomalous Hall effect because they belong to different
scattering classes
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