8,418 research outputs found
Josephson effect in spin-singlet superconductor/ferromagnetic insulator/spin-triplet superconductor junctions with helical -wave states
We study the Josephson effect in spin-singlet superconductor/helical -wave
superconductor junctions with a ferromagnetic barrier using the quasiclassical
Green function method. It is found that both -type and
-type current-phase relations always exist, irrespective of the gap
symmetries in superconductors. The indispensable condition for the
-type and -type current is that the magnetization must
have a component parallel to the crystallographic or axis, which is
distinct from the case of -wave superconductor described by a
\vect{d}-vector with a uniform direction. The relation between the condition
and the symmetries of the gap functions is analysed. We investigate in detail
the symmetries and the sign reversal of the Josephson current when the
magnetization is rotated.Comment: 9 pages,7 figure
A Local-Global LDA Model for Discovering Geographical Topics from Social Media
Micro-blogging services can track users' geo-locations when users check-in
their places or use geo-tagging which implicitly reveals locations. This "geo
tracking" can help to find topics triggered by some events in certain regions.
However, discovering such topics is very challenging because of the large
amount of noisy messages (e.g. daily conversations). This paper proposes a
method to model geographical topics, which can filter out irrelevant words by
different weights in the local and global contexts. Our method is based on the
Latent Dirichlet Allocation (LDA) model but each word is generated from either
a local or a global topic distribution by its generation probabilities. We
evaluated our model with data collected from Weibo, which is currently the most
popular micro-blogging service for Chinese. The evaluation results demonstrate
that our method outperforms other baseline methods in several metrics such as
model perplexity, two kinds of entropies and KL-divergence of discovered
topics
Anderson Impurity in Helical Metal
We use a trial wave function to study the spin-1/2 Kondo effect of a helical
metal on the surface of a three-dimensional topological insulator. While the
impurity spin is quenched by conduction electrons, the spin-spin correlation of
the conduction electron and impurity is strongly anisotropic in both spin and
spatial spaces. As a result of strong spin-orbit coupling, the out-of-plane
component of the impurity spin is found to be fully screened by the orbital
angular momentum of the conduction electrons.Comment: The published versio
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