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国家科学评论(英文版)
国家科学评论(英文版)
国家科学评论(英文版)/Journal National Science ReviewCSCDCSTPCD北大核心SCI
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    High-temperature superconductivity up to 223 K in the Al stabilized metastable hexagonal lanthanum superhydride

    Su ChenYingcai QianXiaoli HuangWuhao Chen...
    180-188页
    查看更多>>摘要:As compressed hydrides constantly refresh the records of superconducting critical temperatures(Tc)in the vicinity of room temperature,this further reinforces the confidence to find more high-temperature superconducting hydrides.In this process,metastable phases of superhydrides offer enough possibilities to access superior superconducting properties.Here we report a metastable hexagonal lanthanum superhydride(P63/mmc-LaHi0)stabilized at 146 GPa by introducing an appropriate proportion of Al,which exhibits high-temperature superconductivity with Tc~178 K,and this value is enhanced to a maximum Tc~223 Kat 164 GPa.Ahuge upper critical magnetic field value Hc2(0)reaches 223 T at 146 GPa.The small volume expansion of P63/mmc-(La,Al)H10 compared with the binary LaH10 indicates the possible interstitial sites of Al atoms filling into the La-H lattice,instead of forming conventional ternary alloy-based superhydrides.This work provides a new strategy for metastable high-temperature superconductors through the multiple-element system.

    High-timing-precision detection of single X-ray photons by superconducting nanowires

    Shuya GuoJingrou TanHengbin ZhangJinguang Wang...
    189-198页
    查看更多>>摘要:Precisely acquiring the timing information of individual X-ray photons is important in both fundamental research and practical applications.The timing precision of commonly used X-ray single-photon detectors remains in the range of one hundred picoseconds to microseconds.In this work,we report on high-timing-precision detection of single X-ray photons through the fast transition to the normal state from the superconductive state of superconducting nanowires.We successfully demonstrate a free-running X-ray single-photon detector with a timing resolution of 20.1 ps made of 100-nm-thick niobium nitride film with an active area of 50 μm by 50 μm.By using a repeated differential timing measurement on two adjacent X-ray single-photon detectors,we demonstrate a precision of 0.87 ps in the arrival-time difference of X-ray photon measurements.Therefore,our work significantly enhances the timing precision in X-ray photon counting,opening a new niche for ultrafast X-ray photonics and many associated applications.

    A versatile model with three-dimensional triangular lattice for unconventional transport and various topological effects

    Jing-Yang YouGang SuYuan Ping Feng
    199-209页
    查看更多>>摘要:The finite Berry curvature in topological materials can induce many subtle phenomena,such as the anomalous Hall effect(AHE),spin Hall effect(SHE),anomalous Nernst effect(ANE),non-linear Hall effect(NLHE)and bulk photovoltaic effects.To explore these novel physics as well as their connection and coupling,a precise and effective model should be developed.Here,we propose such a versatile model-a 3D triangular lattice with alternating hopping parameters,which can yield various topological phases,including kagome bands,triply degenerate fermions,double Weyl semimetals and so on.We reveal that this special lattice can present unconventional transport due to its unique topological surface states and the aforementioned topological phenomena,such as AHE,ANE,NLHE and the topological photocurrent effect.In addition,we also provide a number of material candidates that have been synthesized experimentally with this lattice,and discuss two materials,including a non-magnetic triangular system for SHE,NLHE and the shift current,and a ferromagnetic triangular lattice for AHE and ANE.Our work provides an excellent platform,including both the model and materials,for the study of Berry-curvature-related physics.

    Level pinning of anti-PT-symmetric circuits for efficient wireless power transfer

    Zhiwei GuoFengqing YangHaiyan ZhangXian Wu...
    210-219页
    查看更多>>摘要:Wireless power transfer(WPT)technology based on magnetic resonance(a basic physical phenomenon)can directly transfer energy from the source to the load without wires and other physical contacts,and has been successfully applied to implantable medical devices,electric vehicles,robotic arms and other fields.However,due to the frequency splitting of near-field coupling,the resonant WPT system has some unique limitations,such as poor transmission stability and low efficiency.Here,we propose anti-resonance with level pinning for high-performance WPT.By introducing the anti-resonance mode into the basic WPT platform,we uncover the competition between dissipative coupling and coherent coupling to achieve novel level pinning,and construct an effective anti-parity-time(anti-PT)-symmetric non-Hermitian system that is superior to previous PT-symmetric WPT schemes.On the one hand,the eigenvalue of the anti-PT-symmetric system at resonance frequency is always pure real in both strong and weak coupling regions,and can be used to overcome the transmission efficiency decrease caused by weak coupling,as brought about by,for example,a large size ratio of the transmitter to receiver,or a long transmission distance.On the other hand,due to the level pinning effect of the two kinds of coupling mechanisms,the working frequency of the system is guaranteed to be locked,so frequency tracking is not required when the position and size of the receiver change.Even if the system deviates from the matching condition,an efficient WPT can be realized,thereby demonstrating the robustness of the level pinning.The experimental results show that when the size ratio of the transmitter coil to the receiver coil is 4.29(which is in the weak coupling region),the transfer efficiency of the anti-PT-symmetric system is nearly 4.3(3.2)times higher than that of the PT-symmetric system when the matching conditions are satisfied(deviated).With the miniaturization and integration of devices in mind,a synthetic anti-PT-symmetric system is used to realize a robust WPT.Anti-PT-symmetric WPT technology based on the synthetic dimension not only provides a good research platform for the study of abundant non-Hermitian physics,but also provides a means of going beyond traditional near-field applications with resonance mechanisms,such as resonance imaging,wireless sensing and photonic routing.

    Space telescope set to open a new chapter in China's solar research

    Ling Xin
    220-222页

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