57,272 research outputs found
On the Outage Probability of Localization in Randomly Deployed Wireless Networks
This paper analyzes the localization outage probability (LOP), the
probability that the position error exceeds a given threshold, in randomly
deployed wireless networks. Two typical cases are considered: a mobile agent
uses all the neighboring anchors or select the best pair of anchors for
self-localization. We derive the exact LOP for the former case and tight bounds
for the LOP for the latter case. The comparison between the two cases reveals
the advantage of anchor selection in terms of LOP versus complexity tradeoff,
providing insights into the design of efficient localization systems
Spin transverse force and quantum transverse transport
We present a brief review on spin transverse force, which exerts on the spin
as the electron is moving in an electric field. This force, analogue to the
Lorentz force on electron charge, is perpendicular to the electric field and
spin current carried by the electron. The force stems from the spin-orbit
coupling of electrons as a relativistic quantum effect, and could be used to
understand the Zitterbewegung of electron wave packet and the quantum
transverse transport of electron in a heuristic way.Comment: 4 pages, manuscript of invited talk on IAS Workshop on Spintronics at
Nanyang Techological University, Singapore, 200
Finite-temperature conductivity and magnetoconductivity of topological insulators
The electronic transport experiments on topological insulators exhibit a
dilemma. A negative cusp in magnetoconductivity is widely believed as a quantum
transport signature of the topological surface states, which are immune from
localization and exhibit the weak antilocalization. However, the measured
conductivity drops logarithmically when lowering temperature, showing a typical
feature of the weak localization as in ordinary disordered metals. Here, we
present a conductivity formula for massless and massive Dirac fermions as a
function of magnetic field and temperature, by taking into account the
electron-electron interaction and quantum interference simultaneously. The
formula reconciles the dilemma by explicitly clarifying that the temperature
dependence of the conductivity is dominated by the interaction while the
magnetoconductivity is mainly contributed by the quantum interference. The
theory paves the road to quantitatively study the transport in topological
insulators and other two-dimensional Dirac-like systems, such as graphene,
transition metal dichalcogenides, and silicene.Comment: 5 pages, 5 figure
Extrinsic anomalous Hall conductivity of a topologically nontrivial conduction band
A key step towards dissipationless transport devices is the quantum anomalous
Hall effect, which is characterized by an integer quantized Hall conductance in
a ferromagnetic insulator with strong spin-orbit coupling. In this work, the
anomalous Hall effect due to the impurity scattering, namely the extrinsic
anomalous Hall effect, is studied when the Fermi energy crosses with the
topologically nontrivial conduction band of a quantum anomalous Hall system.
Two major extrinsic contributions, the side-jump and skew-scattering Hall
conductivities, are calculated using the diagrammatic techniques in which both
nonmagnetic and magnetic scattering are taken into account simultaneously. The
side-jump Hall conductivity changes its sign at a critical sheet carrier
density for the nontrivial phase, while it remains sign unchanged for the
trivial phase. The critical sheet carrier densities estimated with realistic
parameters lie in an experimentally accessible range. The results imply that a
quantum anomalous Hall system could be identified in the good-metal regime.Comment: 5 pages, 4 figure
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