Anderson Localization from Berry-Curvature Interchange in Quantum Anomalous Hall System

We theoretically investigate the localization mechanism of the quantum anomalous Hall effect (QAHE) in the presence of spin-flip disorders. We show that the QAHE keeps quantized at weak disorders, then enters a Berry-curvature mediated metallic phase at moderate disorders, and finally goes into the Anderson insulating phase at strong disorders. From the phase diagram, we find that at the charge neutrality point although the QAHE is most robust against disorders, the corresponding metallic phase is much easier to be localized into the Anderson insulating phase due to the \textit{interchange} of Berry curvatures carried respectively by the conduction and valence bands. At the end, we provide a phenomenological picture related to the topological charges to better understand the underlying physical origin of the QAHE Anderson localization.Comment: 6 pages, 4 figure

Detector-decoy high-dimensional quantum key distribution

The decoy-state high-dimensional quantum key distribution provides a practical secure way to share more private information with high photon-information efficiency. In this paper, based on detector-decoy method, we propose a detector-decoy high-dimensional quantum key distribution protocol. Employing threshold detectors and a variable attenuator, we can estimate single-photon fraction of postselected events and Eves Holevo information under the Gaussian collective attack with much simpler operations in practical implementation. By numerical evaluation, we show that without varying source intensity and optimizing decoy-state intensity, our protocol could perform much better than one-decoy-state protocol and as well as the two-decoy-state protocol. Specially, when the detector efficiency is lower, the advantage of the detector-decoy method becomes more prominent

Observation of the zero Hall plateau in a quantum anomalous Hall insulator

Quantum anomalous Hall (QAH) effect in magnetic topological insulator (TI) is a novel transport phenomenon in which the Hall resistance reaches the quantum plateau in the absence of external magnetic field. Recently, this exotic effect has been discovered experimentally in an ultrathin film of the Bi2Te3 family TI with spontaneous ferromagnetic (FM) order. An important question concerning the QAH state is whether it is simply a zero-magnetic-field version of the quantum Hall (QH) effect, or if there is new physics beyond the conventional paradigm. Here we report experimental investigations on the quantum phase transition between the two opposite Hall plateaus of a QAH insulator caused by magnetization reversal. We observe a well-defined plateau with zero Hall conductivity over a range of magnetic field around coercivity, consistent with a recent theoretical prediction. The features of the zero Hall plateau are shown to be closely related to that of the QAH effect, but its temperature evolution exhibits quantitative differences from the network model for conventional QH plateau transition. We propose that the chiral edge states residing at the magnetic domain boundaries, which are unique to a QAH insulator, are responsible for the zero Hall plateau. The rich magnetic domain dynamics makes the QAH effect a distinctive class of quantum phenomenon that may find novel applications in spintronics.Comment: 4 figures, supplementary information include

Artifactual pyrosequencing reads in multiple-displacement-amplified sediment metagenomes from the Red Sea

The Multiple Displacement Amplification (MDA) protocol is reported to introduce different artifacts into DNA samples with impurities. In this study, we report an artifactual effect of MDA with sediment DNA samples from a deep-sea brine basin in the Red Sea. In the metagenomes, we showed the presence of abundant artifactual 454 pyrosequencing reads over sizes of 50 to 220 bp. Gene fragments translocated from neighboring gene regions were identified in these reads. Occasionally, the translocation occurred between the gene fragments from different species. Reads containing these gene fragments could form a strong stem-loop structure. More than 60% of the artifactual reads could fit the structural models. MDA amplification is probably responsible for the massive generation of the artifactual reads with the secondary structure in the metagenomes. Possible sources of the translocations and structures are discussed