Nature, Volume 620 Issue 7972, 3 August 2023

《自然》第620卷，7972期，2023年8月3日

物理学Physics

A rotating white dwarf shows different compositions on its opposite faces

一颗旋转白矮星相对面呈现不同成分

▲ 作者：Ilaria Caiazzo, Kevin B. Burdge, Dayal Wickramasinghe, Vikram S. Dhillon, Stuart P. Littlefair, James Munday, Ingrid Pelisoli, Daniel Perley, Dave I. Sahman

▲ 链接：

https://www.nature.com/articles/s41586-023-06171-9

▲ 摘要：

白矮星是大多数恒星死亡后留下的密度极高的残留物，其质量与太阳质量相当，可压缩成类地行星大小。

研究者报告了对ZTF J203349.8+322901.1的观测，这是一颗过渡白矮星，有两个面：其大气层一面由氢主导，另一面由氦主导。这种特殊性质可能是由一个小磁场的存在引起的，在其表面上造成了温度、压力或混合强度的不均匀性。

ZTF J203349.8+322901.1可能是一类磁性过渡白矮星中最极端的成员，与其类似的还有白矮星GD 323，后者显示出与此相似但更微妙的变化。这类白矮星有助于揭示白矮星光谱演化背后的物理机制。

▲ Abstract：

White dwarfs, the extremely dense remnants left behind by most stars after their death, are characterized by a mass comparable to that of the Sun compressed into the size of an Earth-like planet. Here we report observations of ZTF?J203349.8+322901.1, a transitioning white dwarf with two faces: one side of its atmosphere is dominated by hydrogen and the other one by helium. This peculiar nature is probably caused by the presence of a small magnetic field, which creates an inhomogeneity in temperature, pressure or mixing strength over the surface. ZTF?J203349.8+322901.1 might be the most extreme member of a class of magnetic, transitioning white dwarfs—together with GD?323, a white dwarf that shows similar but much more subtle variations. This class of white dwarfs could help shed light on the physical mechanisms behind the spectral evolution of white dwarfs.

3D integration enables ultralow-noise isolator-free lasers in silicon photonics

3D集成让硅光子学中超低噪声无隔离器激光器成为可能

▲ 作者：Chao Xiang, Warren Jin, Osama Terra, Bozhang Dong, Heming Wang, Lue Wu, Joel Guo, Theodore J. Morin, Eamonn Hughes, Jonathan Peters, Qing-Xin Ji, Avi Feshali, Mario Paniccia, Kerry J. Vahala & John E. Bowers

▲ 链接：

https://www.nature.com/articles/s41586-023-06251-w

▲ 摘要：

光子集成电路广泛应用于电信和数据中心互连等领域。然而，在诸如微波合成器、光学陀螺仪和原子钟等光学系统中，光子集成电路尽管在尺寸、重量、功耗和成本方面具有优势，但仍被认为是次等的解决方案。

这种高精度和高度相干的应用有利于超低噪声激光源与其他光子元件以紧凑而坚固的排列形式集成在一起——即在单个芯片上——用于光子集成电路，以取代大块的光学和光纤。有两个主要问题阻碍了这种设想的光子集成电路的实现：半导体激光器的高相位噪声和在芯片上直接集成光隔离器的困难。

研究者通过利用三维集成来挑战这种惯例，从而产生具有无隔离器操作的硅光子学超低噪声激光器。由于超高质量因子腔，研究所演示的光子集成电路进入了一种不需要光隔离器而产生超低噪声激光器和微波合成器的状态。

这种光子集成电路还为复杂功能和批量生产提供了优越的可扩展性，并随着时间的推移提高了稳定性和可靠性。超低损耗光子集成电路的三维集成标志着向硅基复杂系统和网络迈出了关键的一步。

▲ Abstract：

Photonic integrated circuits are widely used in applications such as telecommunications and data-centre interconnects. However, in optical systems such as microwave synthesizers, optical gyroscopes and atomic clocks, photonic integrated circuits are still considered inferior solutions despite their advantages in size, weight, power consumption and cost. Such high-precision and highly coherent applications favour ultralow-noise laser sources to be integrated with other photonic components in a compact and robustly aligned format—that is, on a single chip—for photonic integrated circuits to replace bulk optics and fibres. There are two major issues preventing the realization of such envisioned photonic integrated circuits: the high phase noise of semiconductor lasers and the difficulty of integrating optical isolators directly on-chip. Here we challenge this convention by leveraging three-dimensional integration that results in ultralow-noise lasers with isolator-free operation for silicon photonics. Through multiple monolithic and heterogeneous processing sequences, direct on-chip integration of III–V gain medium and ultralow-loss silicon nitride waveguides with optical loss around 0.5?decibels per metre are demonstrated. Consequently, the demonstrated photonic integrated circuit enters a regime that gives rise to ultralow-noise lasers and microwave synthesizers without the need for optical isolators, owing to the ultrahigh-quality-factor cavity. Such photonic integrated circuits also offer superior scalability for complex functionalities and volume production, as well as improved stability and reliability over time. The three-dimensional integration on ultralow-loss photonic integrated circuits thus marks a critical step towards complex systems and networks on silicon.

化学Chemistry

Ultrafast deposition of faceted lithium polyhedra by outpacing SEI formation

锂多面体的超快沉积

▲ 作者：Xintong Yuan, Bo Liu, Matthew Mecklenburg & Yuzhang Li

▲ 链接：

https://www.nature.com/articles/s41586-023-06235-w

▲ 摘要：

电沉积锂（Li）金属对高能电池至关重要。然而，同时形成的表面腐蚀膜——固体电解质界面（SEI）使沉积过程复杂化，这使得对锂金属电沉积的理解很差。研究者通过在超快沉积电流密度下超越SEI形成，同时避免质量输运限制，将这两个交织在一起的过程解耦。

通过使用低温电子显微镜，研究者发现金属锂的内在沉积形态是一个菱形十二面体，这是令人惊讶的独立于电解质化学或电流集电极衬底。

在硬币电池结构中，这些菱形十二面体与电流收集器表现出接近点接触的连接，这可以加速非活性锂的形成。研究者提出了一种脉冲电流方案，通过利用锂菱形十二面体作为成核种子来克服这种失效模式，使致密锂的后续生长与基线相比提高了电池性能。

虽然在过去的研究中，锂沉积和SEI形成一直紧密相连，但新实验方法为从根本上理解这些相互分离的过程提供了新的机会，并为设计更好的电池带来了新的见解。

▲ Abstract：

Electrodeposition of lithium (Li) metal is critical for high-energy batteries. However, the simultaneous formation of a surface corrosion film termed the solid electrolyte interphase (SEI) complicates the deposition process, which underpins our poor understanding of Li metal electrodeposition. Here we decouple these two intertwined processes by outpacing SEI formation at ultrafast deposition current densities while also avoiding mass transport limitations. By using cryogenic electron microscopy, we discover the intrinsic deposition morphology of metallic Li to be that of a rhombic dodecahedron, which is surprisingly independent of electrolyte chemistry or current collector substrate. In a coin cell architecture, these rhombic dodecahedra exhibit near point-contact connectivity with the current collector, which can accelerate inactive Li formation8. We propose a pulse-current protocol that overcomes this failure mode by leveraging Li rhombic dodecahedra as nucleation seeds, enabling the subsequent growth of dense Li that improves battery performance compared with a baseline. While Li deposition and SEI formation have always been tightly linked in past studies, our experimental approach enables new opportunities to fundamentally understand these processes decoupled from each other and bring about new insights to engineer better batteries.

Synthesis and properties of cyclic sandwich compounds

环状夹层化合物的合成及性质

▲ 作者：Luca Münzfeld, Sebastian Gillhuber, Adrian Hauser, Sergei Lebedkin, Pauline H?dinger, Nicolai D. Kn?fel, Christina Zovko, Michael T. Gamer, Florian Weigend, Manfred M. Kappes & Peter W. Roesky

▲ 链接：

https://www.nature.com/articles/s41586-023-06192-4

▲ 摘要：

状纳米夹层配合物由单个构建块组装而成。研究者展示了设计、合成和表征一个同构系列的圆形夹心化合物，其术语为“环茂烯”。这些环烯烃由18个重复单元组成，在固体状态下形成几乎理想的圆形封闭环。

量子化学计算认为，离子金属-配体键之间的独特相互作用，配体系统的体积和环闭合时的能量增益，这是由色散相互作用的关键影响，促进了这些循环系统的形成。

到目前为止，只有线性一维多层夹层化合物被研究用于纳米线等潜在应用。这个教科书式的环状夹层化合物的例子有望为进一步创新新的功能有机金属材料打开大门。

▲ Abstract：

Cyclic nanometre-scale sandwich complexes assembled from individual building blocks were synthesized.Here we show the design, synthesis and characterization of an isomorphous series of circular sandwich compounds, for which the term ‘cyclocenes’ is suggested. These cyclocenes consist of 18 repeating units, forming almost ideally circular, closed rings in the solid state, that can be described by the general formula . Quantum chemical calculations lead to the conclusion that a unique interplay between the ionic metal-to-ligand bonds, the bulkiness of the ligand system and the energy gain on ring closure, which is crucially influenced by dispersion interactions, facilitate the formation of these cyclic systems. Up to now, only linear one-dimensional multidecker sandwich compounds have been investigated for possible applications such as nanowires. This textbook example of cyclic sandwich compounds is expected to open the door for further innovations towards new functional organometallic materials.

地质和气候Climate & Geology

Remote detection of a lunar granitic batholith at Compton–Belkovich

月球花岗岩基的远程探测

▲ 作者：Matthew A. Siegler, Jianqing Feng, Katelyn Lehman-Franco, Jeffery C. Andrews-Hanna, Rita C. Economos, Michael St. Clair, Chase Million, James W. Head, Timothy D. Glotch & Mackenzie N. White

▲ 链接：

https://www.nature.com/articles/s41586-023-06183-5

▲ 摘要：

除了地球，太阳系中几乎没有花岗岩。在岩浆系统中获得花岗岩组成需要多阶段的熔融和分选，这也增加了放射性成因元素的浓度。地球上丰富的水和板块构造促进了这些过程，帮助重新融化。

虽然在月球上没有这些驱动因素，但已经发现了小的花岗岩样本，但它们的起源和它们所代表的系统规模的细节是未知的。研究者报告了一个异常热地热源的微波波长测量，最好的解释是在富钍的远侧特征康普顿-贝尔科维奇下面存在一个直径约50公里的花岗岩系统。被动微波辐射测量对多个波长深度的综合热梯度很敏感。

嫦娥一号和嫦娥二号微波仪器的3 - 37千兆赫天线温度能够测量到每平方米约180毫瓦的峰值热通量，这大约是月球高地平均热通量的20倍。这一惊人的规模和地理范围表明，在月球上，特别是在Procellarum地区之外，存在一个类似地球的、进化的花岗岩系统，其规模比人们认为的要大得多。

此外，这些方法是可推广的：类似被动辐射测量数据的使用可以极大地扩展我们对月球和其他行星上地热过程的认识。

▲ Abstract：

Granites are nearly absent in the Solar System outside of Earth. Achieving granitic compositions in magmatic systems requires multi-stage melting and fractionation, which also increases the concentration of radiogenic elements. Abundant water and plate tectonics facilitate these processes on Earth, aiding in remelting. Although these drivers are absent on the Moon, small granite samples have been found, but details of their origin and the scale of systems they represent are unknown. Here we report microwave-wavelength measurements of an anomalously hot geothermal source that is best explained by the presence of an approximately 50-kilometre-diameter granitic system below the thorium-rich farside feature known as Compton–Belkovich. Passive microwave radiometry is sensitive to the integrated thermal gradient to several wavelengths depth. The 3–37-gigahertz antenna temperatures of the Chang’e-1 and Chang’e-2 microwave instruments allow us to measure a peak heat flux of about 180?milliwatts per square metre, which is about 20 times higher than that of the average lunar highlands3,4. The surprising magnitude and geographic extent of this feature imply an Earth-like, evolved granitic system larger than believed possible on the Moon, especially outside of the Procellarum region5. Furthermore, these methods are generalizable: similar uses of passive radiometric data could vastly expand our knowledge of geothermal processes on the Moon and other planetary bodies.

Fennoscandian tree-ring anatomy shows a warmer modern than medieval climate

树木年轮解剖显示，现代气候比中世纪气候更温暖

▲ 作者：Jesper Bj?rklund, Kristina Seftigen, Markus Stoffel, Marina V. Fonti, Sven Kottlow, David C. Frank, Jan Esper, Patrick Fonti, Hugues Goosse, H?kan Grudd, Bj?rn E. Gunnarson, Daniel Nievergelt, Elena Pellizzari, Marco Carrer & Georg von Arx

▲ 链接：

https://www.nature.com/articles/s41586-023-06176-4

▲ 摘要：

地球系统模型和各种气候代理来源表明，全球变暖至少在公元前是前所未有的。研究利用树木年轮发现，芬诺斯坎迪亚半岛当前的气候比中世纪时期的气候要温暖得多。这突出了即使在区域尺度上，人为强迫在气候变暖中的主导作用，从而调和了重建和模式模拟之间的不一致。

研究者使用每年解决1170年的树木年轮记录，该记录完全依赖于松树的管状解剖测量，提供了温暖季节仪器温度变化的高保真测量。

因此，他们呼吁建立更多这样的千年记录，以进一步提高对历史和未来气候变化的认识，减少区域间乃至全球尺度上的不确定性。

▲ Abstract：

Earth system models and various climate proxy sources indicate global warming is unprecedented during at least the Common Era. Here we show that the current climate of the Fennoscandian Peninsula is substantially warmer than that of the medieval period. This highlights the dominant role of anthropogenic forcing in climate warming even at the regional scale, thereby reconciling inconsistencies between reconstructions and model simulations. We used an annually resolved 1,170-year-long tree-ring record that relies exclusively on tracheid anatomical measurements from Pinus sylvestris trees, providing high-fidelity measurements of instrumental temperature variability during the warm season. We therefore call for the construction of more such millennia-long records to further improve our understanding and reduce uncertainties around historical and future climate change at inter-regional and eventually global scales.