自然科学经典对照版（自然20220818出版一周论文导读）

自然科学经典对照版（自然20220818出版一周论文导读）https://www.nature.com/articles/s41586-022-04970-0▲ 链接：Self-oscillating pump in a topological dissipative atom–cavity system拓扑耗散原子-腔系统中的自振荡泵浦▲ 作者：Davide Dreon Alexander Baumg?rtner Xiangliang Li Simon Hertlein Tilman Esslinger & Tobias Donner

编译 | 未玖

Nature 18 August 2022 VOL 608 ISSUE 7923

《自然》2022年8月18日，第608卷，7923期

物理学Physics

Self-oscillating pump in a topological dissipative atom–cavity system

拓扑耗散原子-腔系统中的自振荡泵浦

▲ 作者：Davide Dreon Alexander Baumg?rtner Xiangliang Li Simon Hertlein Tilman Esslinger & Tobias Donner

▲ 链接：

https://www.nature.com/articles/s41586-022-04970-0

▲ 摘要：

泵浦是一种传输机制，其中直流电由电势的循环演变产生。如Thouless泵浦所示，当考虑量子粒子在时空周期势中的运动时，泵浦过程可能具有拓扑起源。然而，驱动这些泵浦的周期性演化一直被认为是从外部传递的，正如迄今为止研究的实验系统。

研究组报道了一种泵浦耦合到光学谐振器的量子气体涌现机制，在不使用周期性驱动的情况下观察粒子电流。原子所经历的泵浦电势由自洽腔场干扰驱动原子的静态激光场形成。

由于耗散，腔场在其两个正交之间演化，每个正交对应于不同的中心对称晶体构型。这种自振荡产生了一种时间周期势，类似于拓扑紧束缚模型中描述电子输运的势，如典型的Rice-Mele泵。

在实验中，研究组通过测量腔场相对于驱动场的相位绕组并在原位观察原子运动，直接跟踪这一演化过程。观察到的机制结合了拓扑系统和开放系统的动力学，并具有连续耗散时间晶体的特征。

▲ Abstract：

Pumps are transport mechanisms in which direct currents result from a cyclic evolution of the potential. As Thouless showed the pumping process can have topological origins when considering the motion of quantum particles in spatially and temporally periodic potentials. However the periodic evolution that drives these pumps has always been assumed to be imparted from outside as has been the case in the experimental systems studied so far. Here we report on an emergent mechanism for pumping in a quantum gas coupled to an optical resonator where we observe a particle current without applying a periodic drive. The pumping potential experienced by the atoms is formed by the self-consistent cavity field interfering with the static laser field driving the atoms. Owing to dissipation the cavity field evolves between its two quadratures each corresponding to a different centrosymmetric crystal configuration. This self-oscillation results in a time-periodic potential analogous to that describing the transport of electrons in topological tight-binding models such as the paradigmatic Rice–Mele pump. In the experiment we directly follow the evolution by measuring the phase winding of the cavity field with respect to the driving field and observing the atomic motion in situ. The observed mechanism combines the dynamics of topological and open systems and features characteristics of continuous dissipative time crystals.

Formation of moiré interlayer excitons in space and time

莫尔层间激子的时空形成

▲ 作者：David Schmitt Jan Philipp Bange Wiebke Bennecke AbdulAziz AlMutAIri Giuseppe Meneghini Kenji Watanabe et al.

▲ 链接：

https://www.nature.com/articles/s41586-022-04977-7

▲ 摘要：

原子厚度范德华异质结构中的莫尔超晶格在延长控制电子和谷电子寿命、人工莫尔晶格中的激子约束以及奇异量子相形成方面具有巨大的前景。这种莫尔诱导的涌现现象对于层间激子尤其强烈，其中空穴和电子位于异质结构的不同层中。为了充分挖掘相关莫尔和激子物理的潜力，必须深入了解超快层间激子形成过程和实空间波函数约束。

研究组通过飞秒光电发射动量显微镜提供了对莫尔层间激子这些关键属性的定量访问。首先，阐明了层间激子主要通过飞秒激子-声子散射和随后在层间杂化∑谷处的电荷转移而形成；其次，证明了层间激子具有动量指纹，这是超晶格莫尔改性的直接标志；第三，重建了激子电子部分的波函数分布，并将其尺寸与实空间莫尔超晶格进行了比较。

该研究工作提供了在时空上直接访问层间激子形成动力学的途径，并揭示了研究相关莫尔和激子物理的机会，以助力未来实现物质的奇异量子相。

▲ Abstract：

Moiré superlattices in atomically thin van der Waals heterostructures hold great promise for extended control of electronic and valleytronic lifetimes the confinement of excitons in artificial moiré lattices and the formation of exotic quantum phases. Such moiré-induced emergent phenomena are particularly strong for interlayer excitons where the hole and the electron are localized in different layers of the heterostructure. To exploit the full potential of correlated moiré and exciton physics a thorough understanding of the ultrafast interlayer exciton formation process and the real-space wavefunction confinement is indispensable. Here we show that femtosecond photoemission momentum microscopy provides quantitative access to these key properties of the moiré interlayer excitons. First we elucidate that interlayer excitons are dominantly formed through femtosecond exciton–phonon scattering and subsequent charge transfer at the interlayer-hybridized Σ valleys. Second we show that interlayer excitons exhibit a momentum fingerprint that is a direct hallmark of the superlattice moiré modification. Third we reconstruct the wavefunction distribution of the electronic part of the exciton and compare the size with the real-space moiré superlattice. Our work provides direct access to interlayer exciton formation dynamics in space and time and reveals opportunities to study correlated moiré and exciton physics for the future realization of exotic quantum phases of matter.

信息科学Information Science

A compute-in-memory chip based on resistive random-access memory

基于电阻性随机存取存储器的内存计算芯片

▲ 作者：Weier Wan Rajkumar Kubendran Clemens Schaefer Sukru Burc Eryilmaz Wenqiang Zhang Dabin Wu et al.

▲ 链接：

https://www.nature.com/articles/s41586-022-04992-8

▲ 摘要：

直接在边缘设备上实现日益复杂的人工智能（AI）功能要求边缘硬件具有前所未有的能效。基于电阻性随机存取存储器（RRAM）的内存计算（CIM）有望满足此类需求，通过将AI模型权重存储在密集、模拟和非易失性RRAM设备中，并在RRAM内直接执行AI计算，从而消除单独计算和内存之间耗电的数据移动。

尽管最近研究证明了在完全集成的RRAM-CIM硬件上的内存矩阵向量乘法，但RRAM-CIM芯片的目标仍是同时提供高能效、支持多种模型的通用性和媲美软件的准确性。尽管效率、通用性和准确性对于广泛采用该技术来说都不可或缺，但它们之间相互关联的权衡不能通过对设计的任何单个抽象级别的单一改进来解决。

通过对从算法和架构到电路和设备的所有设计层次上进行协同优化，研究组提出了NeuRRAM（一种基于RRAM的CIM芯片），为不同模型架构重新配置CIM核心的同时提供了通用性，在不同计算位精度上的能效比以前最先进的RRAM-CIM芯片优两倍，推理精度可与在各种AI任务中量化为4位权重的软件模型相媲美，其中MNIST和CIFAR-10图像分类的准确率分别为99.0%与85.7%，谷歌语音命令识别的正确率为84.7%，在贝叶斯图像恢复任务中，图像重建误差减少了70%。

▲ Abstract：

Realizing increasingly complex artificial intelligence (AI) functionalities directly on edge devices calls for unprecedented energy efficiency of edge hardware. Compute-in-memory (CIM) based on resistive random-access memory (RRAM) promises to meet such demand by storing AI model weights in dense analogue and non-volatile RRAM devices and by performing AI computation directly within RRAM thus eliminating power-hungry data movement between separate compute and memory. Although recent studies have demonstrated in-memory matrix-vector multiplication on fully integrated RRAM-CIM hardware it remains a goal for a RRAM-CIM chip to simultaneously deliver high energy efficiency versatility to support diverse models and software-comparable accuracy. Although efficiency versatility and accuracy are all indispensable for broad adoption of the technology the inter-related trade-offs among them cannot be addressed by isolated improvements on any single abstraction level of the design. Here by co-optimizing across all hierarchies of the design from algorithms and architecture to circuits and devices we present NeuRRAM—a RRAM-based CIM chip that simultaneously delivers versatility in reconfiguring CIM cores for diverse model architectures energy efficiency that is two-times better than previous state-of-the-art RRAM-CIM chips across various computational bit-precisions and inference accuracy comparable to software models quantized to four-bit weights across various AI tasks including accuracy of 99.0?percent on MNIST and 85.7-percent on CIFAR-10 image classification 84.7-percent accuracy on Google speech command recognition and a 70-percent reduction in image-reconstruction error on a Bayesian image-recovery task.

材料科学Materials Science

Preservation of high-pressure volatiles in nanostructured diamond capsules

纳米结构金刚石胶囊中保存高压挥发物

▲ 作者：Zhidan Zeng Jianguo Wen Hongbo Lou Xin Zhang Liuxiang Yang Lijie Tan et al.

▲ 链接：

https://www.nature.com/articles/s41586-022-04955-z

▲ 摘要：

高压会导致冷凝挥发物发生剧烈变化和新现象，从压力容器回收后通常无法保存。

研究组报道了一种将挥发物加压至1型玻璃碳前驱体纳米孔中的过程，通过加热将玻璃碳转化为纳米晶体金刚石，并合成能够在高压下永久保存挥发物的独立纳米结构金刚石胶囊（NDC），即使释放回环境条件下也可用于各种基于真空的诊断探针（包括电子显微镜）。

作为演示，研究组对保存在NDC中的高压氩气样品进行了全面研究。同步X射线衍射和高分辨率透射电子显微镜显示，纳米晶金刚石中嵌入了约22.0 GPa的纳米级氩晶体，能量色散X射线光谱提供了定量成分分析，电子能量损失光谱详细描述了高压氩气的化学键合性质。

通过控制NDC合成压力可调节NDC内氩气样品的保存压力。为了测试NDC工艺的普遍适用性，研究组证明了高压氖也可以被捕获在NDC中，且?2型玻璃碳可用作前驱体容器材料。对其他挥发物和碳同素异形体的进一步实验，有望使高压探索与主流凝聚态物质研究和应用相提并论。

▲ Abstract：

High pressure induces dramatic changes and novel phenomena in condensed volatiles that are usually not preserved after recovery from pressure vessels. Here we report a process that pressurizes volatiles into nanopores of type 1 glassy carbon precursors converts glassy carbon into nanocrystalline diamond by heating and synthesizes free-standing nanostructured diamond capsules (NDCs) capable of permanently preserving volatiles at high pressures even after release back to ambient conditions for various vacuum-based diagnostic probes including electron microscopy. As a demonstration we perform a comprehensive study of a high-pressure argon sample preserved in NDCs. Synchrotron X-ray diffraction and high-resolution transmission electron microscopy show nanometre-sized argon crystals at around 22.0?gigapascals embedded in nanocrystalline diamond energy-dispersive X-ray spectroscopy provides quantitative compositional analysis and electron energy-loss spectroscopy details the chemical bonding nature of high-pressure argon. The preserved pressure of the argon sample inside NDCs can be tuned by controlling NDC synthesis pressure. To test the general applicability of the NDC process we show that high-pressure neon can also be trapped in NDCs and that type?2 glassy carbon can be used as the precursor container material. Further experiments on other volatiles and carbon allotropes open the possibility of bringing high-pressure explorations on a par with mainstream condensed-matter investigations and applications.

Floating perovskite-BiVO4 devices for scalable solar fuel production

可扩展太阳能燃料生产的漂浮钙钛矿-BiVO4器件

▲ 作者：Virgil Andrei Geani M. Ucoski Chanon Pornrungroj Chawit Uswachoke Qian Wang Demetra S. Achilleos et al.

▲ 链接：

https://www.nature.com/articles/s41586-022-04978-6

▲ 摘要：

光电化学（PEC）人工叶通过将采光和催化集成在一个紧凑设备中，具有降低可持续太阳能燃料生产成本的潜力。然而，当前的沉积技术限制了其可扩展性，而脆弱和沉重的块体材料可能会影响其运输和部署。

研究组展示了通过使用薄而柔性的基底和碳质保护层制造轻质人工叶。沉积在铟锡氧化物包覆的聚对苯二甲酸乙二醇酯上的卤化铅钙钛矿光电阴极，使用铂催化剂时活性达到4266μmol H2g−1h−1 ，而使用分子Co催化剂还原CO2的光电阴极在低（0.1太阳）光照下的CO:H2选择性高达7.2。

相应的轻质钙钛矿-BiVO4 PEC器件显示无辅助太阳能-燃料效率分别为0.58%（H2）和0.053%（CO）。100cm2的独立人工叶证明了它们可扩展的潜力，性能和稳定性（约24h）可与1.7cm2的同类物相媲美。

运行中形成的气泡进一步使30-100mg cm−2 的设备漂浮，而轻型反应器便于在河流中户外试验时收集气体。这种叶子状的PEC装置填补了传统太阳能燃料方法之间的重量鸿沟，每克展示的活性可与光催化悬浮液和植物叶子相媲美。

这种轻型漂浮系统可实现开放水域应用，从而避免与土地使用相竞争。

▲ Abstract：

Photoelectrochemical (PEC) artificial leaves hold the potential to lower the costs of sustainable solar fuel production by integrating light harvesting and catalysis within one compact device. However current deposition techniques limit their scalability whereas fragile and heavy bulk materials can affect their transport and deployment. Here we demonstrate the fabrication of lightweight artificial leaves by employing thin flexible substrates and carbonaceous protection layers. Lead halide perovskite photocathodes deposited onto indium tin oxide-coated polyethylene terephthalate achieved an activity of 4 266 μmol H2g−1h−1 using a platinum catalyst whereas photocathodes with a molecular Co catalyst for CO2 reduction attained a high CO:H2 selectivity of 7.2 under lower (0.1 sun) irradiation. The corresponding lightweight perovskite-BiVO4 PEC devices showed unassisted solar-to-fuel efficiencies of 0.58% (H2) and 0.053% (CO) respectively. Their potential for scalability is demonstrated by 100cm‍2 stand-alone artificial leaves which sustained a comparable performance and stability (of approximately 24h) to their 1.7cm2 counterparts. Bubbles formed under operation further enabled 30–100 mg cm−2 devices to float while lightweight reactors facilitated gas collection during outdoor testing on a river. This leaf-like PEC device bridges the gulf in weight between traditional solar fuel approaches showcasing activities per gram comparable to those of photocatalytic suspensions and plant leaves. The presented lightweight floating systems may enable open-water applications thus avoiding competition with land use.

地球科学Earth Science

Continental configuration controls ocean oxygenation during the Phanerozoic

显生宙大陆构造控制着海洋氧合作用

▲ 作者：Alexandre Pohl Andy Ridgwell Richard G. Stockey Christophe Thomazo Andrew Keane Emmanuelle Vennin et al.

▲ 链接：

https://www.nature.com/articles/s41586-022-05018-z

▲ 摘要：

海洋动物的早期进化和大部分灭绝史被认为由海洋中溶解氧浓度（[O2]）变化所驱动。反过来，[O2]被广泛认为受大气氧（pO2）地质历史主导。

研究组通过一系列地球系统模型实验展示了显生宙期间大陆重排如何驱动海洋氧合的深刻变化，并导致上层海洋和海底[O2]时间上的基本解耦。他们进一步确认了全球海洋环流中存在状态转变，这导致显生宙早期甚至在现代pO2条件下广泛的深海缺氧。

研究组关于海洋氧合在稳定千年（kyr）周期内波动的发现还提供了一种因果机制，可解释早期古生代后生动物辐射率和灭绝率的升高。在该模型中，全球气候和海洋通风之间缺乏任何简单关联，且海洋氧合发生的深刻变化与大气pO2无关，这对海洋氧化还原替代物的解释提出了质疑，但也指出了大陆构造在生物圈演化中迄今被忽略的作用。

▲ Abstract：

The early evolutionary and much of the extinction history of marine animals is thought to be driven by changes in dissolved oxygen concentrations ([O2]) in the ocean. In turn [O2] is widely assumed to be dominated by the geological history of atmospheric oxygen (pO2). Here by contrast we show by means of a series of Earth system model experiments how continental rearrangement during the Phanerozoic Eon drives profound variations in ocean oxygenation and induces a fundamental decoupling in time between upper-ocean and benthic [O2]. We further identify the presence of state transitions in the global ocean circulation which lead to extensive deep-ocean anoxia developing in the early Phanerozoic even under modern pO2. Our finding that ocean oxygenation oscillates over stable thousand-year (kyr) periods also provides a causal mechanism that might explain elevated rates of metazoan radiation and extinction during the early Palaeozoic Era. The absence in our modelling of any simple correlation between global climate and ocean ventilation and the occurrence of profound variations in ocean oxygenation independent of atmospheric pO2 presents a challenge to the interpretation of marine redox proxies but also points to a hitherto unrecognized role for continental configuration in the evolution of the biosphere.