物理学Physics

▲ 作者：Thomas P. Greene, Taylor J. Bell, Elsa Ducrot, Achrène Dyrek, Pierre-Olivier Lagage & Jonathan J. Fortney

▲ 链接：

https://www.nature.com/articles/s41586-023-05951-7

▲ 摘要：

红矮星TRAPPIST-1系统因其七颗行星而引人注目，这些行星在大小、质量、密度和恒星加热方面与太阳系中的岩石行星金星、地球和火星相似。科学家对所有TRAPPIST-1行星通过哈勃或斯皮策太空望远镜的透射光谱进行了观测，但尚未发现大气特征或受到强烈限制。TRAPPIST-1b是该系统中距离M矮星最近的行星，它接收到的辐射是地球从太阳接收到的辐射的四倍。这种相对较大的恒星加热表明它的热辐射是可以测量的。

研究者利用詹姆斯•韦伯太空望远镜中红外仪器的F1500W滤光片，对地球大小的系外行星TRAPPIST-1 b进行了光度观测。他们在5次观测中发现了次日食，当所有数据合并时，置信度为8.7σ。这些测量结果与TRAPPIST-1恒星入射通量的再辐射最一致，这些再辐射仅来自行星的白天半球。最直接的解释是，很少或根本没有行星大气重新分配来自主星的辐射，也没有可探测到的大气吸收二氧化碳或其他物质。

▲ Abstract：

The TRAPPIST-1 system is remarkable for its seven planets that are similar in size, mass, density and stellar heating to the rocky planets Venus, Earth and Mars in the Solar System. All the TRAPPIST-1 planets have been observed with transmission spectroscopy using the Hubble or Spitzer space telescopes, but no atmospheric features have been detected or strongly constrained. TRAPPIST-1 b is the closest planet to the M-dwarf star of the system, and it receives four times as much radiation as Earth receives from the Sun. This relatively large amount of stellar heating suggests that its thermal emission may be measurable. Here we present photometric secondary eclipse observations of the Earth-sized exoplanet TRAPPIST-1 b using the F1500W filter of the mid-infrared instrument on the James Webb Space Telescope (JWST). We detect the secondary eclipses in five separate observations with 8.7σ confidence when all data are combined. These measurements are most consistent with re-radiation of the incident flux of the TRAPPIST-1 star from only the dayside hemisphere of the planet. The most straightforward interpretation is that there is little or no planetary atmosphere redistributing radiation from the host star and also no detectable atmospheric absorption of carbon dioxide (CO2) or other species.

▲ 作者：Jacob L. Bean, Qiao Xue, Prune C. August, Jonathan Lunine, Michael Zhang, Daniel Thorngren, Shang-Min Tsai, Keivan G. Stassun, Everett Schlawin, Eva-Maria Ahrer, Jegug Ih & Megan Mansfield

▲ 链接：

https://www.nature.com/articles/s41586-023-05984-y

▲ 摘要：

大气中的金属富集（即比氦重的元素，也称为“金属丰度”）是巨行星形成的关键判断指标。太阳系的巨行星的质量与它们的体积金属丰度和大气金属丰度呈反比关系。系外巨行星的质量与总体金属含量也呈反比关系。

然而，在这种关系中存在着显著的分散，并且不知道大气金属丰度如何与行星质量或总体金属丰度相关。作者证明了土星质量系外行星HD 149026b的大气金属丰度是太阳的59~276倍，这比土星的大气金属丰度大约是太阳的7.5倍要大。这一结果是基于詹姆斯•韦伯太空望远镜测量的行星热辐射光谱中二氧化碳和水的吸收特征的建模。

HD 149026b是已知的金属含量最高的巨行星，估计其质量的总体重元素丰度为66±2%。作者发现HD 149026b和太阳系巨行星的大气金属丰度与总体金属丰度的关系大于与行星质量的关系。

▲ Abstract：

Atmospheric metal enrichment (that is, elements heavier than helium, also called ‘metallicity’) is a key diagnostic of the formation of giant planets. The giant planets of the Solar System show an inverse relationship between mass and both their bulk metallicities and atmospheric metallicities. Extrasolar giant planets also display an inverse relationship between mass and bulk metallicity. However, there is significant scatter in the relationship and it is not known how atmospheric metallicity correlates with either planet mass or bulk metallicity. Here we show that the Saturn-mass exoplanet HD 149026b has an atmospheric metallicity 59–276 times solar (at 1σ), which is greater than Saturn’s atmospheric metallicity of roughly 7.5 times solar10 at more than 4σ confidence. This result is based on modelling CO₂ and H₂O absorption features in the thermal emission spectrum of the planet measured by the James Webb Space Telescope. HD 149026b is the most metal-rich giant planet known, with an estimated bulk heavy element abundance of 66 ± 2% by mass. We find that the atmospheric metallicities of both HD 149026b and the Solar System giant planets are more correlated with bulk metallicity than planet mass.

▲ 作者：Tolulope M. Ajayi, Nozomi Shirato, Tomas Rojas, Sarah Wieghold, Xinyue Cheng, Kyaw Zin Latt, Daniel J. Trainer, Naveen K. Dandu, Yiming Li, Sineth Premarathna, Sanjoy Sarkar, Daniel Rosenmann, Yuzi Liu, Nathalie Kyritsakas, Shaoze Wang, Eric Masson, Volker Rose, Xiaopeng Li, Anh T. Ngo & Saw-Wai Hla

▲ 链接：

https://www.nature.com/articles/s41586-023-06011-w

▲ 摘要：

自从1895年伦琴发现X射线以来，它的应用已经无处不在，从医学和环境应用到材料科学。X射线表征需要大量的原子，减少材料的数量是一个长期的目标。作者证明了X射线可以用来表征一个原子的元素和化学状态。

使用一个专门的尖端作为探测器，可以检测到由铁原子和铽原子与有机配体配合产生的X射线激发电流。在X射线吸收光谱中，铁原子的L_2,3和铽原子的M_4,5吸收边信号的指纹清晰可见。这些原子的化学状态是用近边X射线吸收信号来表征的，其中X射线激发共振隧穿（X-ERT）对铁原子起主导作用。

只有当尖端位于原子的正上方且距离极近时，才能检测到X射线信号，这证实了在隧穿状态下的原子局域检测。该将同步加速器X射线与量子隧穿过程联系起来，为在最终单原子极限下同时表征材料的元素和化学性质开辟了未来的X射线实验。

▲ Abstract：

Since the discovery of X-rays by Roentgen in 1895, its use has been ubiquitous, from medical and environmental applications to materials sciences. X-ray characterization requires a large number of atoms and reducing the material quantity is a long-standing goal. Here we show that X-rays can be used to characterize the elemental and chemical state of just one atom. Using a specialized tip as a detector, X-ray-excited currents generated from an iron and a terbium atom coordinated to organic ligands are detected. The fingerprints of a single atom, the L_2,3 and M_4,5 absorption edge signals for iron and terbium, respectively, are clearly observed in the X-ray absorption spectra. The chemical states of these atoms are characterized by means of near-edge X-ray absorption signals, in which X-ray-excited resonance tunnelling (X-ERT) is dominant for the iron atom. The X-ray signal can be sensed only when the tip is located directly above the atom in extreme proximity, which confirms atomically localized detection in the tunnelling regime. Our work connects synchrotron X-rays with a quantum tunnelling process and opens future X-rays experiments for simultaneous characterizations of elemental and chemical properties of materials at the ultimate single-atom limit.

化学Chemistry

▲ 作者：Tingting Song, Zibin Chen, Xiangyuan Cui, Shenglu Lu, Hansheng Chen, Hao Wang, Tony Dong, Bailiang Qin, Kang Cheung Chan, Milan Brandt, Xiaozhou Liao, Simon P. Ringer & Ma Qian

▲ 链接：

https://www.nature.com/articles/s41586-023-05952-6

▲ 摘要：

钛合金是一种先进的轻质材料，在许多关键应用中不可或缺。钛工业的支柱是α -β钛合金，它是通过添加合金来稳定α和β相而制成的。研究者重点利用两种最强大的稳定元素和α -β钛合金的强化剂，氧和铁，这两种元素很容易丰富。然而，氧的脆化作用（俗称为“钛的氪石”）和铁的微偏析阻碍了它们的结合，从而无法发展出强韧的α -β钛-氧-铁合金。

研究者将合金设计与增材制造工艺设计相结合，展示了一系列具有出色拉伸性能的钛-氧-铁组合物。他们使用各种表征技术解释这些性质的原子尺度起源。氧和铁的丰度以及增材制造净形或近净形的工艺简单性使这些α -β钛-氧-铁合金具有广泛的应用前景。此外，它们为大规模利用工业废弃物劣质海绵钛或海绵钛氧铁提供了希望，减少能源密集型海绵钛生产的碳足迹的经济和环境潜力是巨大的。

▲ Abstract：

Titanium alloys are advanced lightweight materials, indispensable for many critical applications. The mainstay of the titanium industry is the α–β titanium alloys, which are formulated through alloying additions that stabilize the α and β phases. Our work focuses on harnessing two of the most powerful stabilizing elements and strengtheners for α–β titanium alloys, oxygen and iron, which are readily abundant. However, the embrittling effect of oxygen, described colloquially as ‘the kryptonite to titanium’, and the microsegregation of iron have hindered their combination for the development of strong and ductile α–β titanium–oxygen–iron alloys. Here we integrate alloy design with additive manufacturing (AM) process design to demonstrate a series of titanium–oxygen–iron compositions that exhibit outstanding tensile properties. We explain the atomic-scale origins of these properties using various characterization techniques. The abundance of oxygen and iron and the process simplicity for net-shape or near-net-shape manufacturing by AM make these α–β titanium–oxygen–iron alloys attractive for a diverse range of applications. Furthermore, they offer promise for industrial-scale use of off-grade sponge titanium or sponge titanium–oxygen–iron, an industrial waste product at present. The economic and environmental potential to reduce the carbon footprint of the energy-intensive sponge titanium production is substantial.

▲ 作者：Joseph A. Mattocks, Jonathan J. Jung, Chi-Yun Lin, Ziye Dong, Neela H. Yennawar, Emily R. Featherston, Christina S. Kang-Yun, Timothy A. Hamilton, Dan M. Park, Amie K. Boal & Joseph A. Cotruvo Jr

▲ 链接：

https://www.nature.com/articles/s41586-023-05945-5

▲ 摘要：

众所周知，技术上至关重要的稀土元素很难分离，因为它们的离子半径和配位数存在细微差异。天然镧系结合蛋白lanmodulin（LanM）是传统溶剂萃取分离的可持续替代品。

作者研究了一种新的LanM （Hans-LanM），它具有对稀土离子半径敏感的低聚态，镧（III）诱导的二聚体比镝（III）诱导的二聚体紧密100倍以上。X射线晶体结构说明了镧（III）和镝（III）之间的皮米尺度半径差异是如何通过羧酸盐位移（重新排列第二球氢键网络）传播到Hans-LanM的四元结构中的。

研究揭示了不同的金属配位策略，使Hans-LanM在稀土元素中具有更高的选择性。这项工作展示了选择性镧系元素识别基序的自然多样性，并揭示了稀土敏感二聚化作为一种生物学原理，通过该原理可以调节基于生物分子的分离过程的性能。

▲ Abstract：

Technologically critical rare-earth elements are notoriously difficult to separate, owing to their subtle differences in ionic radius and coordination number. The natural lanthanide-binding protein lanmodulin (LanM) is a sustainable alternative to conventional solvent-extraction-based separation. Here we characterize a new LanM, from Hansschlegelia quercus (Hans-LanM), with an oligomeric state sensitive to rare-earth ionic radius, the lanthanum(III)-induced dimer being &>100-fold tighter than the dysprosium(III)-induced dimer. X-ray crystal structures illustrate how picometre-scale differences in radius between lanthanum(III) and dysprosium(III) are propagated to Hans-LanM’s quaternary structure through a carboxylate shift that rearranges a second-sphere hydrogen-bonding network. Comparison to the prototypal LanM from Methylorubrum extorquens reveals distinct metal coordination strategies, rationalizing Hans-LanM’s greater selectivity within the rare-earth elements. This work showcases the natural diversity of selective lanthanide recognition motifs, and it reveals rare-earth-sensitive dimerization as a biological principle by which to tune the performance of biomolecule-based separation processes.

▲ 作者：Kaichen Zhu, Sebastian Pazos, Fernando Aguirre, Yaqing Shen, Yue Yuan, Wenwen Zheng, Osamah Alharbi, Marco A. Villena, Bin Fang, Xinyi Li, Alessandro Milozzi, Matteo Farronato, Miguel Muñoz-Rojo, Tao Wang, Ren Li, Hossein Fariborzi, Juan B. Roldan, Guenther Benstetter, Xixiang Zhang, Husam N. Alshareef, Tibor Grasser, Huaqiang Wu, Daniele Ielmini & Mario Lanza

▲ 链接：

https://www.nature.com/articles/s41586-023-05973-1

▲ 摘要：

利用二维材料的优异电子特性制造先进的电子电路是半导体工业的主要目标。然而，该领域的大多数研究都局限于在无功能SiO₂-Si衬底上制造和表征孤立的大型（大于1平方微米）器件。一些研究将单层石墨烯集成在硅微芯片上，作为大面积（超过500平方微米）的互连和大型晶体管的通道（约16.5平方微米），但集成密度都很低，没有计算证明，而操纵单层二维材料具有挑战性，因为在传递过程中，天然的针孔和裂缝增加了可变性，降低了成品率。

研究者提出了用于记忆体应用的高集成密度二维CMOS混合微芯片的制造（CMOS代表互补金属氧化物半导体）。他们将一层多层六方氮化硼转移到含有180 纳米节点CMOS晶体管的硅微芯片的后端互连上，并通过对顶部电极和互连进行图像化来完成电路。CMOS晶体管对六方氮化硼忆阻器的电流提供了出色的控制，这使得能够在0.053平方微米的忆阻器中实现约500万次的循环。

研究者通过构建逻辑门来演示内存计算，并测量适合于实现尖峰神经网络的与尖峰时间相关的可塑性信号。实现的高性能和相对较高的技术就绪水平代表了在微电子产品和记忆应用中集成二维材料的显着进步。

▲ Abstract：

Exploiting the excellent electronic properties of two-dimensional (2D) materials to fabricate advanced electronic circuits is a major goal for the semiconductor industry. However, most studies in this field have been limited to the fabrication and characterization of isolated large (more than 1 µm²) devices on unfunctional SiO₂–Si substrates. Some studies have integrated monolayer graphene on silicon microchips as a large-area (more than 500 µm²) interconnection3 and as a channel of large transistors (roughly 16.5 µm²), but in all cases the integration density was low, no computation was demonstrated and manipulating monolayer 2D materials was challenging because native pinholes and cracks during transfer increase variability and reduce yield. Here, we present the fabrication of high-integration-density 2D–CMOS hybrid microchips for memristive applications—CMOS stands for complementary metal–oxide–semiconductor. We transfer a sheet of multilayer hexagonal boron nitride onto the back-end-of-line interconnections of silicon microchips containing CMOS transistors of the 180 nm node, and finalize the circuits by patterning the top electrodes and interconnections. The CMOS transistors provide outstanding control over the currents across the hexagonal boron nitride memristors, which allows us to achieve endurances of roughly 5 million cycles in memristors as small as 0.053 µm². We demonstrate in-memory computation by constructing logic gates, and measure spike-timing dependent plasticity signals that are suitable for the implementation of spiking neural networks. The high performance and the relatively-high technology readiness level achieved represent a notable advance towards the integration of 2D materials in microelectronic products and memristive applications.