5,364 research outputs found
Anomalous spin Hall effects in Dresselhaus (110) quantum wells
Anomalous spin Hall effects that belong to the intrinsic type in Dresselhaus
(110) quantum wells are discussed. For the out-of-plane spin component,
antisymmetric current-induced spin polarization induces opposite spin Hall
accumulation, even though there is no spin-orbit force due to Dresselhaus (110)
coupling. A surprising feature of this spin Hall induction is that the spin
accumulation sign does not change upon bias reversal. Contribution to the spin
Hall accumulation from the spin Hall induction and the spin deviation due to
intrinsic spin-orbit force as well as extrinsic spin scattering, can be
straightforwardly distinguished simply by reversing the bias. For the inplane
component, inclusion of a weak Rashba coupling leads to a new type of
intrinsic spin Hall effect solely due to spin-orbit-force-driven spin
separation.Comment: 6 pages, 5 figure
Spin-dependent Klein tunneling in graphene: Role of Rashba spin-orbit coupling
Within an effective Dirac theory the low-energy dispersions of monolayer
graphene in the presence of Rashba spin-orbit coupling and spin-degenerate
bilayer graphene are described by formally identical expressions. We explore
implications of this correspondence for transport by choosing chiral tunneling
through pn and pnp junctions as a concrete example. A real-space Green's
function formalism based on a tight-binding model is adopted to perform the
ballistic transport calculations, which cover and confirm previous theoretical
results based on the Dirac theory. Chiral tunneling in monolayer graphene in
the presence of Rashba coupling is shown to indeed behave like in bilayer
graphene. Combined effects of a forbidden normal transmission and spin
separation are observed within the single-band n to p transmission regime. The
former comes from real-spin conservation, in analogy with pseudospin
conservation in bilayer graphene, while the latter arises from the intrinsic
spin-Hall mechanism of the Rashba coupling.Comment: 10 pages, 10 figure
Efficient quantum transport simulation for bulk graphene heterojunctions
The quantum transport formalism based on tight-binding models is known to be
powerful in dealing with a wide range of open physical systems subject to
external driving forces but is, at the same time, limited by the memory
requirement's increasing with the number of atomic sites in the scattering
region. Here we demonstrate how to achieve an accurate simulation of quantum
transport feasible for experimentally sized bulk graphene heterojunctions at a
strongly reduced computational cost. Without free tuning parameters, we show
excellent agreement with a recent experiment on Klein backscattering [A. F.
Young and P. Kim, Nature Phys. 5, 222 (2009)].Comment: 5 pages, 3 figure
Diquark mass differences from unquenched lattice QCD
We calculate diquark correlation functions in the Landau gauge on the lattice
using overlap valence quarks and 2+1-flavor domain wall fermion configurations.
Quark masses are extracted from the scalar part of quark propagators in the
Landau gauge. Scalar diquark quark mass difference and axial vector scalar
diquark mass difference are obtained for diquarks composed of two light quarks
and of a strange and a light quark. Light sea quark mass dependence of the
results is examined. Two lattice spacings are used to check the discretization
effects. The coarse and fine lattices are of sizes and
with inverse spacings and , respectively.Comment: 9 figure
Temporal similarity metrics for latent network reconstruction: The role of time-lag decay
When investigating the spreading of a piece of information or the diffusion
of an innovation, we often lack information on the underlying propagation
network. Reconstructing the hidden propagation paths based on the observed
diffusion process is a challenging problem which has recently attracted
attention from diverse research fields. To address this reconstruction problem,
based on static similarity metrics commonly used in the link prediction
literature, we introduce new node-node temporal similarity metrics. The new
metrics take as input the time-series of multiple independent spreading
processes, based on the hypothesis that two nodes are more likely to be
connected if they were often infected at similar points in time. This
hypothesis is implemented by introducing a time-lag function which penalizes
distant infection times. We find that the choice of this time-lag strongly
affects the metrics' reconstruction accuracy, depending on the network's
clustering coefficient and we provide an extensive comparative analysis of
static and temporal similarity metrics for network reconstruction. Our findings
shed new light on the notion of similarity between pairs of nodes in complex
networks
- …