|《自然》（20210624出版）一周论文导读_

编译 | 冯维维
Nature, 24 June 2021 , Volume 594 Issue 7864
《自然》2021年6月24日，第594卷， 7864期

本文图片

物理学Physics
Past, present and future stars that can see Earth as a transiting exoplanet
过去，现在和未来看到地球作为过境系外行星的恒星
作者：L. KalteneggerJ. K. Faherty
链接：
https://www.nature.com/articles/s41586-021-03596-y
摘要
在宇宙中寻找生命的过程中，凌日系外行星是目前的最佳目标。随着数千个行星已经被探测到，搜寻工作正进入一个新的发现时代，即将推出的大型望远镜将在过境星球的大气层中寻找“生命”的迹象。
作者报告了自早期人类文明（约5000年前）以来，在距离太阳100秒差距内的1715颗恒星的正确位置，它们可以在过渡地球上发现生命，另外还有319颗恒星将在未来5000年进入这个特殊的有利位置。
在这些恒星中，有7颗已知的系外行星，包括曾观测到地球凌日的罗斯-128 ，还有蒂加登的恒星和特拉普斯特-1 ，它们将分别在29年和1642年后观测到地球。作者发现，人造无线电波已经扫过了榜单上离地球最近的75颗恒星。
Abstract
In the search for life in the cosmos, transiting exoplanets are currently our best targets. With thousands already detected, our search is entering a new era of discovery with upcoming large telescopes that will look for signs of ‘life’ in the atmospheres of transiting worlds. Here we report that 1,715 stars within 100 parsecs from the Sun are in the right position to have spotted life on a transiting Earth since early human civilization (about 5,000 years ago), with an additional 319 stars entering this special vantage point in the next 5,000 years. Among these stars are seven known exoplanet hosts, including Ross-128, which saw Earth transit the Sun in the past, and Teegarden’s Star and Trappist-1, which will start to see it in 29 and 1,642 years, respectively. We found that human-made radio waves have already swept over 75 of the closest stars on our list.
Accurately computing the electronic properties of a quantum ring
精确计算量子环的电子性质
【|《自然》（20210624出版）一周论文导读】作者：C. Neill, T. McCourt, V. Smelyanskiy, etc.
链接：
https://www.nature.com/articles/s41586-021-03576-2
摘要
研究凝聚态系统的一个很有前途的方法是在一个设计好的量子平台上模拟它们。然而，迄今为止还没有达到优于经典方法所需的精度。作者使用18个超导量子位元，为一个精确的凝聚态模拟器提供了一个实验蓝图，并演示了如何研究基本的电子性质。
作者通过重建一维线的单粒子带结构来确定基本方法的基准。他们演示了几乎完全的消相干和读出错误，并测量了导线的能量特征值，误差约为0.01 rad ，而典型的能量尺度为1 rad 。通过强调傅里叶变换的鲁棒性，包括在统计不确定性为10 - 4 rad的情况下解析特征能量的能力，可以深入了解该算法的保真度。作者还综合了磁通和无序局域势这两个凝聚态系统的关键原理。当清扫磁通量时，我们观察到频谱中避免的水平交叉，提供了局部无序的空间分布的详细指纹。
通过结合这些方法，作者重建了本征态的电子性质，观察了持续的电流和附加的无序对电导的强抑制。他们表示，这项研究描述了一种精确的量子模拟方法，为研究具有超导量子位的新量子材料铺平了道路。
Abstract
A promising approach to study condensed-matter systems is to simulate them on an engineered quantum platform. However, the accuracy needed to outperform classical methods has not been achieved so far. Here, using 18 superconducting qubits, we provide an experimental blueprint for an accurate condensed-matter simulator and demonstrate how to investigate fundamental electronic properties. We benchmark the underlying method by reconstructing the single-particle band structure of a one-dimensional wire. We demonstrate nearly complete mitigation of decoherence and readout errors, and measure the energy eigenvalues of this wire with an error of approximately 0.01 rad, whereas typical energy scales are of the order of 1 rad. Insight into the fidelity of this algorithm is gained by highlighting the robust properties of a Fourier transform, including the ability to resolve eigenenergies with a statistical uncertainty of 10 - 4 rad. We also synthesize magnetic flux and disordered local potentials, which are two key tenets of a condensed-matter system. When sweeping the magnetic flux we observe avoided level crossings in the spectrum, providing a detailed fingerprint of the spatial distribution of local disorder. By combining these methods we reconstruct electronic properties of the eigenstates, observing persistent currents and a strong suppression of conductance with added disorder. Our work describes an accurate method for quantum simulation5,6 and paves the way to study new quantum materials with superconducting qubits.
材料学Mateirial
Fizeau drag in graphene plasmonics
菲索拖曳石墨烯等离子体
作者：Y. Dong, L. Xiong, I. Y. Phinney, Z. Sun, R. Jing, A. S. McLeod, S. Zhang, S. Liu, F. L. Ruta, H. Gao, Z. Dong, R. Pan, J. H. Edgar, P. Jarillo-Herrero, L. S. Levitov, A. J. Millis, M. M. Fogler, D. A. BandurinD. N. Basov
链接：
https://www.nature.com/articles/s41586-021-03640-x
摘要
菲涅耳预测了移动介质对光的拖曳作用，菲索著名的流水实验证实了这一点。这一重大发现是爱因斯坦狭义相对论的实验基石之一，并在相对论运动学的背景下得到了很好的理解。相比之下，关于电子流在固体中拖曳光子的实验充满了不一致性，到目前为止还未能与该理论达成一致。
作者报道了石墨烯中红外光子和电子的混合准粒子——表面等离子体激元（SPPs）的电子流拖曳。阻力是直接可视化的红外纳米成像传播等离子体波存在高密度电流。石墨烯中的极化子对着漂移载流子传播时，其波长会缩短。与光的菲索效应不同，由电流产生的SPP拖拽无法用简单的运动学解释，它与石墨烯中狄拉克电子的非线性电动力学有关。
他们表示，观测到的等离子体菲索拖拽使红外频率上的时间反转对称性和互易性得以打破，而无需借助磁场或手性光泵浦。菲索阻力也为研究电子液体中的相互作用和非平衡效应提供了一个工具。
Abstract
Dragging of light by moving media was predicted by Fresnel and verified by Fizeau’s celebrated experiments with flowing water. This momentous discovery is among the experimental cornerstones of Einstein’s special relativity theory and is well understood in the context of relativistic kinematics. By contrast, experiments on dragging photons by an electron flow in solids are riddled with inconsistencies and have so far eluded agreement with the theory. Here we report on the electron flow dragging surface plasmon polaritons (SPPs): hybrid quasiparticles of infrared photons and electrons in graphene. The drag is visualized directly through infrared nano-imaging of propagating plasmonic waves in the presence of a high-density current. The polaritons in graphene shorten their wavelength when propagating against the drifting carriers. Unlike the Fizeau effect for light, the SPP drag by electrical currents defies explanation by simple kinematics and is linked to the nonlinear electrodynamics of Dirac electrons in graphene. The observed plasmonic Fizeau drag enables breaking of time-reversal symmetry and reciprocity at infrared frequencies without resorting to magnetic fields or chiral optical pumping. The Fizeau drag also provides a tool with which to study interactions and nonequilibrium effects in electron liquids.
Efficient Fizeau drag from Dirac electrons in monolayer graphene
单层石墨烯中狄拉克电子的有效菲索阻力
作者：Wenyu Zhao, Sihan Zhao, Hongyuan Li, Sheng Wang, Shaoxin Wang, M. Iqbal Bakti Utama, Salman Kahn, Yue Jiang, Xiao Xiao, SeokJae Yoo, Kenji Watanabe, Takashi Taniguchi, Alex ZettlFeng Wang
链接：
https://www.nature.com/articles/s41586-021-03574-4
摘要
菲索在1850年证明了光在运动介质中传播时的速度是可以改变的。然而，这种对光速的控制并没有在快速移动的电子介质中通过电流来有效地实现。本文报道了利用无质量狄拉克电子的高电子迁移率和缓慢的等离子体传播，直接观察到强偏置单层石墨烯中等离子体激元的菲索拖动。石墨烯中的大偏置电流产生了一个快速漂移的狄拉克电子介质，容纳了等离子激元。这导致了非互反的等离子体传播，等离子体与漂移的电子介质一起以增强的速度传播。
作者利用低温近场红外纳米技术测量多普勒位移等离子体波长，直接成像偏置石墨烯中的等离子体激元模式。他们观察到与漂移电子介质一起运动的等离子体和与漂移电子介质对抗运动的等离子体之间的等离子体波长差异高达3.6% 。作者在等离子体多普勒效应上的发现，为非平衡系统中非互反表面等离子体激元的电气控制提供了机会。
Abstract
Fizeau demonstrated in 1850 that the speed of light can be modified when it is propagating in moving media. However, such control of the light speed has not been achieved efficiently with a fast-moving electron media by passing an electrical current. Here we report direct observation of Fizeau drag of plasmon polaritons in strongly biased monolayer graphene by exploiting the high electron mobility and the slow plasmon propagation of massless Dirac electrons. The large bias current in graphene creates a fast-drifting Dirac electron medium hosting the plasmon polariton. This results in non-reciprocal plasmon propagation, where plasmons moving with the drifting electron media propagate at an enhanced speed. We measure the Doppler-shifted plasmon wavelength using cryogenic near-field infrared nanoscopy, which directly images the plasmon polariton mode in the biased graphene at low temperature. We observe a plasmon wavelength difference of up to 3.6 per cent between a plasmon moving with and a plasmon moving against the drifting electron media. Our findings on the plasmonic Doppler effect provide opportunities for electrical control of non-reciprocal surface plasmon polaritons in non-equilibrium systems.
化学Chemistry
Operando optical tracking of single-particle ion dynamics in batteries
电池中单粒子离子动力学的操作性光学跟踪
作者：Alice J. Merryweather, Christoph Schnedermann, Quentin Jacquet, Clare P. GreyAkshay Rao
链接：
https://www.nature.com/articles/s41586-021-03584-2
摘要
发展锂离子电池技术的关键——尤其是快速充电——是在现实条件下、实时地在纳米到中尺度上跟踪和理解功能材料中发生的动态过程的能力。电池运行期间的锂离子动态成像（操作成像）目前需要复杂的同步X射线或电子技术，这并不适合高通量材料筛选。这限制了快速和合理的材料改进。
作者介绍了一种简单的基于实验室的光学干涉散射显微镜，用于解析电池材料中的纳米锂离子动力学，并将其应用于跟踪电极基质中典型正极材料LixCoO2的单个粒子的循环。作者直接可视化绝缘体到金属、固溶体和锂有序相变，并确定锂在单粒子水平上的扩散率，识别不同的充放电机制。最后，作者捕获了Li0.5CoO2组分中与单斜晶格畸变相关的不同晶体取向间畴界的动态形成。
作者表示，该方法的高通量特性允许在整个电极上取样许多粒子，未来将有助于探索位错、形态和循环速率对电池退化的作用。其成像概念的通用性意味着它可以应用于任何电池电极的研究，更广泛的是，它可以应用于离子传输与电子或结构变化相关的系统。这些系统包括纳米离子薄膜、离子导电聚合物、光催化材料和记忆电阻器。
Abstract
The key to advancing lithium-ion battery technology—in particular, fast charging—is the ability to follow and understand the dynamic processes occurring in functioning materials under realistic conditions, in real time and on the nano- to mesoscale. Imaging of lithium-ion dynamics during battery operation (operando imaging) at present requires sophisticated synchrotron X-ray or electron techniques, which do not lend themselves to high-throughput material screening. This limits rapid and rational materials improvements. Here we introduce a simple laboratory-based, optical interferometric scattering microscope to resolve nanoscopic lithium-ion dynamics in battery materials, and apply it to follow cycling of individual particles of the archetypal cathode material, LixCoO2, within an electrode matrix. We visualize the insulator-to-metal, solid solution and lithium ordering phase transitions directly and determine rates of lithium diffusion at the single-particle level, identifying different mechanisms on charge and discharge. Finally, we capture the dynamic formation of domain boundaries between different crystal orientations associated with the monoclinic lattice distortion at the Li0.5CoO2 composition16. The high-throughput nature of our methodology allows many particles to be sampled across the entire electrode and in future will enable exploration of the role of dislocations, morphologies and cycling rate on battery degradation. The generality of our imaging concept means that it can be applied to study any battery electrode, and more broadly, systems where the transport of ions is associated with electronic or structural changes. Such systems include nanoionic films, ionic conducting polymers, photocatalytic materials and memristors.
A catalysis-driven artificial molecular pump
催化驱动的人工分子泵
作者：Shuntaro Amano, Stephen D. P. FieldenDavid A. Leigh
链接：
https://www.nature.com/articles/s41586-021-03575-3
摘要
所有的生物泵都是自动催化剂；它们通过利用化学燃料催化分解所释放的能量来维持电池的不平衡状态。到目前为止，已经报道了许多人工分子泵，但它们都是由光驱动的，或需要重复连续添加试剂，或在每个循环中改变电势来操作。
作者描述了一个自主的化学燃料信息棘轮，在燃料存在的情况下，冠醚大环从体积溶液泵到分子轴上，而不需要进一步干预。该机制利用冠醚在轴上的位置，既可以在螺纹时促进其后面的屏障附着，又可以抑制随后的屏障清除，直到环迁移到集水区。调整这两个过程的动态使分子机器能够连续地从体积溶液中的最低能量状态泵入轴上的更高能量状态。在
屏障形成和清除连续发生的条件下，通过连续泵送多达三个宏循环到轴上，实验证明了棘轮作用。只要没有反应的燃料存在，不平衡的（n）轮烷（n到4）就会一直存在，之后轮烷环会慢慢脱线。利用催化技术驱动人工分子泵，在催化与分子机械的界面上开辟了新的机遇、新的见解和新的研究方向。
Abstract
All biological pumps are autonomous catalysts; they maintain the out-of-equilibrium conditions of the cell by harnessing the energy released from their catalytic decomposition of a chemical fuel. A number of artificial molecular pumps have been reported to date, but they are all either fuelled by light or require repetitive sequential additions of reagents or varying of an electric potential during each cycle to operate. Here we describe an autonomous chemically fuelled information ratchet that in the presence of fuel continuously pumps crown ether macrocycles from bulk solution onto a molecular axle without the need for further intervention. The mechanism uses the position of a crown ether on an axle both to promote barrier attachment behind it upon threading and to suppress subsequent barrier removal until the ring has migrated to a catchment region. Tuning the dynamics of both processes enables the molecular machine to pump macrocycles continuously from their lowest energy state in bulk solution to a higher energy state on the axle. The ratchet action is experimentally demonstrated by the progressive pumping of up to three macrocycles onto the axle from bulk solution under conditions where barrier formation and removal occur continuously. The out-of-equilibrium [n]rotaxanes (characterized with n up to 4) are maintained for as long as unreacted fuel is present, after which the rings slowly de-thread. The use of catalysis to drive artificial molecular pumps opens up new opportunities, insights and research directions at the interface of catalysis and molecular machinery.
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