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