原文地址：http://news.sciencenet.cn/htmlnews/2023/12/514778.shtm
編譯 | 未玖
Nature, 21 December 2023, VOL 624, ISSUE 7992
《自然》2023年12月21日，第624卷，7992期
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物理學Physics
Moiré synaptic transistor with room-temperature neuromorphic functionality
具有室溫神經形態功能的莫爾突觸晶體管
▲ 作者：Xiaodong Yan, Zhiren Zheng, Vinod K. Sangwan, Justin H. Qian, Xueqiao Wang, Stephanie E. Liu, et al.
▲ 鏈接：
https://www.nature.com/articles/s41586-023-06791-1
▲ 摘要：
莫爾量子材料通過扭曲二維異質結構中增強的內部庫侖相互作用，產生了奇異的電子現象。當與原子級薄材料中異常高的靜電控制相結合時，莫爾異質結構有望助力下一代電子設備具有前所未有的功能。然而，盡管人們進行了廣泛探索，莫爾電子現象迄今為止僅限于不切實際的低溫，從而阻礙了莫爾量子材料的實際應用。
研究組報道了基于不對稱雙層石墨烯/六方氮化硼莫爾異質結構的低功率（20 pW）莫爾突觸晶體管的實驗實現和室溫運行。不對稱莫爾電位產生了穩健的電子棘輪態，從而實現了控制器件導電性的電荷載流子滯后、非易失性注入。
雙門控莫爾異質結構中的非對稱門控實現了多種生物仿真神經形態功能，如可重構的突觸響應、基于時空的tempotron和Bienenstock-Cooper-Munro輸入特異性適應。通過這種方式，莫爾突觸晶體管實現了用于人工智能和機器學習的高效內存計算設計和邊緣硬件加速器。
▲ Abstract：
Moiré quantum materials host exotic electronic phenomena through enhanced internal Coulomb interactions in twisted two-dimensional heterostructures. When combined with the exceptionally high electrostatic control in atomically thin materials, moiré heterostructures have the potential to enable next-generation electronic devices with unprecedented functionality. However, despite extensive exploration, moiré electronic phenomena have thus far been limited to impractically low cryogenic temperatures, thus precluding real-world applications of moiré quantum materials. Here we report the experimental realization and room-temperature operation of a low-power (20?pW) moiré synaptic transistor based on an asymmetric bilayer graphene/hexagonal boron nitride moiré heterostructure. The asymmetric moiré potential gives rise to robust electronic ratchet states, which enable hysteretic, non-volatile injection of charge carriers that control the conductance of the device. The asymmetric gating in dual-gated moiré heterostructures realizes diverse biorealistic neuromorphic functionalities, such as reconfigurable synaptic responses, spatiotemporal-based tempotrons and Bienenstock–Cooper–Munro input-specific adaptation. In this manner, the moiré synaptic transistor enables efficient compute-in-memory designs and edge hardware accelerators for artificial intelligence and machine learning.
材料科學Materials Science
Homogenizing out-of-plane cation composition in perovskite solar cells
鈣鈦礦太陽能電池中面外陽離子組成的均勻化
▲ 作者：Zheng Liang, Yong Zhang, Huifen Xu, Wenjing Chen, Boyuan Liu, Jiyao Zhang, et al.
▲ 鏈接：
https://www.nature.com/articles/s41586-023-06784-0
▲ 摘要：
FA1-xCsxPbI3鈣鈦礦太陽能電池中FA為甲脒，為集成高效率、持久穩定性和與大規模制造的兼容性提供了一個有吸引力的選擇。盡管Cs陽離子的引入有望形成完美的鈣鈦礦晶格，但A位陽離子偏析引起的成分不均勻性可能會對太陽能電池的光伏性能造成不利影響。
研究組可視化了鈣鈦礦薄膜沿垂直方向的面外成分不均勻性，并確定了不均勻性的根本原因及其對器件的潛在影響。他們使用1-（苯磺酰基）吡咯設計了一種來均勻化鈣鈦礦薄膜中陽離子組成分布的策略。由此產生的p-i-n器件產生了25.2%的經認證穩態光子-電子轉換效率和持久的穩定性。
▲ Abstract：
Perovskite solar cells with the formula FA1-xCsxPbI3, where FA is formamidinium, provide an attractive option for integrating high efficiency, durable stability and compatibility with scaled-up fabrication. Despite the incorporation of Cs cations, which could potentially enable a perfect perovskite lattice, the compositional inhomogeneity caused by A-site cation segregation is likely to be detrimental to the photovoltaic performance of the solar cells. Here we visualized the out-of-plane compositional inhomogeneity along the vertical direction across perovskite films and identified the underlying reasons for the inhomogeneity and its potential impact for devices. We devised a strategy using 1-(phenylsulfonyl)pyrrole to homogenize the distribution of cation composition in perovskite films. The resultant p–i–n devices yielded a certified steady-state photon-to-electron conversion efficiency of 25.2% and durable stability.
Three-dimensional atomic structure and local chemical order of medium- and high-entropy nanoalloys
中高熵納米合金的三維原子結構和局部化學有序性
▲ 作者：Saman Moniri, Yao Yang, Jun Ding, Yakun Yuan, Jihan Zhou, Long Yang, et al.
▲ 鏈接：
https://www.nature.com/articles/s41586-023-06785-z
▲ 摘要：
中高熵合金（M/HEAs）混合了幾種接近等原子組成的主要元素，代表了一種模式轉換策略，用于設計冶金、催化和其他領域此前未知的材料。M/HEAs的核心假設之一是晶格畸變，已通過不同的數值和實驗技術對其進行了研究。然而，確定M/HEAs中的三維（3D）晶格畸變仍頗具挑戰。
此外，X射線和中子研究、原子模擬、能量色散光譜和電子衍射結果對M/HEAs中假定的隨機元素混合提出了質疑，表明M/HEAs中存在局部化學有序。然而，由于能量色散光譜沿區帶軸將原子柱的組成整合在一起，并且彌漫電子反射可能來自平面缺陷而非局部化學有序，因此對三維局部化學有序的直接實驗觀察一直很困難。
研究組利用原子電子斷層掃描技術確定了M/HEA納米粒子的3D原子位置，并定量表征了局部晶格畸變、應變張量、孿晶邊界、位錯核心和化學近程有序（CSRO）。結果表明，與中熵合金相比，高熵合金具有更大的局部晶格畸變和更多的不均勻應變，且該應變與CSRO有關。
研究組還在中熵合金中觀察到CSRO介導孿晶形成，即孿晶發生在能量較高的CSRO區域，而能量較低的CSRO區域不會引發孿晶，這代表了首次在任何材料中將局部化學有序與結構缺陷關聯起來的實驗觀察。他們希冀這項工作不僅可擴展人們對這類重要材料的基本理解，還將通過工程晶格畸變和局部化學有序為定制M/HEA性能提供基礎。
▲ Abstract：
Medium- and high-entropy alloys (M/HEAs) mix several principal elements with near-equiatomic composition and represent a model-shift strategy for designing previously unknown materials in metallurgy, catalysis and other fields. One of the core hypotheses of M/HEAs is lattice distortion, which has been investigated by different numerical and experimental techniques. However, determining the three-dimensional (3D) lattice distortion in M/HEAs remains a challenge. Moreover, the presumed random elemental mixing in M/HEAs has been questioned by X-ray and neutron studies, atomistic simulations, energy dispersive spectroscopy and electron diffraction, which suggest the existence of local chemical order in M/HEAs. However, direct experimental observation of the 3D local chemical order has been difficult because energy dispersive spectroscopy integrates the composition of atomic columns along the zone axes and diffuse electron reflections may originate from planar defects instead of local chemical order. Here we determine the 3D atomic positions of M/HEA nanoparticles using atomic electron tomography and quantitatively characterize the local lattice distortion, strain tensor, twin boundaries, dislocation cores and chemical short-range order (CSRO). We find that the high-entropy alloys have larger local lattice distortion and more heterogeneous strain than the medium-entropy alloys and that strain is correlated to CSRO. We also observe CSRO-mediated twinning in the medium-entropy alloys, that is, twinning occurs in energetically unfavoured CSRO regions but not in energetically favoured CSRO ones, which represents, to our knowledge, the first experimental observation of correlating local chemical order with structural defects in any material. We expect that this work will not only expand our fundamental understanding of this important class of materials but also provide the foundation for tailoring M/HEA properties through engineering lattice distortion and local chemical order.
化學Chemistry
Autonomous chemical research with large language models
大型語言模型助力自主化學研究
▲ 作者：Daniil A. Boiko, Robert MacKnight, Ben Kline & Gabe Gomes
▲ 鏈接：
https://www.nature.com/articles/s41586-023-06792-0
▲ 摘要：
基于Transformer的大型語言模型在自然語言處理、生物學、化學和計算機編程等各個領域都取得了重大進展。
研究組展示了Coscientist的開發和性能，這是一個由GPT-4驅動的人工智能系統，通過整合互聯網和文檔搜索、代碼執行和實驗自動化等工具授權的大型語言模型，自主設計、計劃和執行復雜的實驗。
Coscientist展示了其在六項不同任務中加速研究的潛力，包括鈀催化交叉偶聯反應的成功優化，同時展示了（半）自主實驗設計和執行的先進能力。該發現表明了像Coscientist這樣的人工智能系統在推進研究方面的多功能性、有效性和可解釋性。
▲ Abstract：
Transformer-based large language models are making significant strides in various fields, such as natural language processing, biology, chemistry and computer programming. Here, we show the development and capabilities of Coscientist, an artificial intelligence system driven by GPT-4 that autonomously designs, plans and performs complex experiments by incorporating large language models empowered by tools such as internet and documentation search, code execution and experimental automation. Coscientist showcases its potential for accelerating research across six diverse tasks, including the successful reaction optimization of palladium-catalysed cross-couplings, while exhibiting advanced capabilities for (semi-)autonomous experimental design and execution. Our findings demonstrate the versatility, efficacy and explainability of artificial intelligence systems like Coscientist in advancing research.
地球科學Earth Science
Biological carbon pump estimate based on multidecadal hydrographic data
基于多年代際水文數據的生物碳泵估算
▲ 作者：Wei-Lei Wang, Weiwei Fu, Frédéric A. C. Le Moigne, Robert T. Letscher, Yi Liu, Jin-Ming Tang, et al.
▲ 鏈接：
https://www.nature.com/articles/s41586-023-06772-4
▲ 摘要：
光合作用從大氣中吸收二氧化碳，產生的有機碳從表層轉移到中層水域。然而，目前基于觀測的估計對這種生物碳泵（BCP）的強度存在分歧。地球系統模型（ESM）也顯示出BCP估算值的廣泛分布，表明已知碳輸出途徑的代表性有限。
研究組使用幾十年的水文觀測，通過一個逆向生物地球化學模型對BCP強度進行了自上而下的估計，該模型隱式解釋了所有已知的輸出途徑。他們估計在73.4 m（模型透光層深度）的總有機碳（TOC）輸出為15.00±1.12 Pg C/年，由于上層水柱中有機質的快速再礦化，只有三分之二的有機碳達到100 m深度。
按透光層以下的固碳時間τ劃分，τ> 3個月的全球有機碳總產率為11.09±1.02 Pg C/年，τ> 1年的總產率降至8.25±0.30 Pg C/年，其中81%由下沉顆粒和垂直遷移浮游動物引起的非平流擴散垂直通量所貢獻。然而，通過溶解物質和懸浮顆粒的混合和其他流體輸送的有機碳輸出對于滿足呼吸性碳需求仍具有區域重要性。
此外，從該反演中推斷出的碳封存效率的溫度依賴性表明，未來全球變暖可能會加強上層海洋有機質的再循環，從而潛在削弱BCP。
▲ Abstract：
The transfer of photosynthetically produced organic carbon from surface to mesopelagic waters draws carbon dioxide from the atmosphere. However, current observation-based estimates disagree on the strength of this biological carbon pump (BCP). Earth system models (ESMs) also exhibit a large spread of BCP estimates, indicating limited representations of the known carbon export pathways. Here we use several decades of hydrographic observations to produce a top-down estimate of the strength of the BCP with an inverse biogeochemical model that implicitly accounts for all known export pathways. Our estimate of total organic carbon (TOC) export at 73.4 m (model euphotic zone depth) is 15.00 ± 1.12 Pg C year 1, with only two-thirds reaching 100 m depth owing to rapid remineralization of organic matter in the upper water column. Partitioned by sequestration time below the euphotic zone, τ, the globally integrated organic carbon production rate with τ > 3 months is 11.09 ± 1.02 Pg C year 1, dropping to 8.25 ± 0.30 Pg C year 1 for τ > 1 year, with 81% contributed by the non-advective-diffusive vertical flux owing to sinking particles and vertically migrating zooplankton. Nevertheless, export of organic carbon by mixing and other fluid transport of dissolved matter and suspended particles remains regionally important for meeting the respiratory carbon demand. Furthermore, the temperature dependence of the sequestration efficiency inferred from our inversion suggests that future global warming may intensify the recycling of organic matter in the upper ocean, potentially weakening the BCP.
社會學Sociology
Human mobility networks reveal increased segregation in large cities
人口流動網絡表明大城市的隔離現象日益嚴重
▲ 作者：Hamed Nilforoshan, Wenli Looi, Emma Pierson, Blanca Villanueva, Nic Fishman, Yiling Chen, et al.
▲ 鏈接：
https://www.nature.com/articles/s41586-023-06757-3
▲ 摘要：
大型、密集和國際化的地區支持社會經濟混合和不同個體之間的接觸，是一個長期愿景。評估該假設一直很困難，因為此前對社會經濟混合的衡量依賴于靜態住宅數據，而不是人們在工作、休閑場所和家庭社區中的真實暴露情況。
研究組開發了一種隔離暴露的測量方法，捕捉了這些日常接觸的社會經濟多樣性。使用手機移動數據來代表美國960萬人中的16億次真實暴露，他們測量了382個大都市統計區（MSAs）和2829個縣的隔離暴露。
結果發現，在10個最大的MSA中，隔離暴露比在居民少于10萬的小型MSA中高出67%。這意味著，與愿景相反，大型國際大都市地區的居民較少接觸到社會經濟多樣化的個體；其次，大城市的社會經濟隔離加劇源于其為特定社會經濟群體提供了更多的差異化空間選擇；第三，當一個城市的中心（如購物中心）被定位為連接不同的社區，從而吸引所有社會經濟地位的人時，這種隔離加劇影響就會被抵消。
該研究結果挑戰了人文地理學中一個長期存在的猜想，并強調了城市設計如何既能防止又能促進不同個體之間的互動。
▲ Abstract：
A long-standing expectation is that large, dense and cosmopolitan areas support socioeconomic mixing and exposure among diverse individuals. Assessing this hypothesis has been difficult because previous measures of socioeconomic mixing have relied on static residential housing data rather than real-life exposures among people at work, in places of leisure and in home neighbourhoods. Here we develop a measure of exposure segregation that captures the socioeconomic diversity of these everyday encounters. Using mobile phone mobility data to represent 1.6 billion real-world exposures among 9.6 million people in the United States, we measure exposure segregation across 382 metropolitan statistical areas (MSAs) and 2,829 counties. We find that exposure segregation is 67% higher in the ten largest MSAs than in small MSAs with fewer than 100,000 residents. This means that, contrary to expectations, residents of large cosmopolitan areas have less exposure to a socioeconomically diverse range of individuals. Second, we find that the increased socioeconomic segregation in large cities arises because they offer a greater choice of differentiated spaces targeted to specific socioeconomic groups. Third, we find that this segregation-increasing effect is countered when a city’s hubs (such as shopping centres) are positioned to bridge diverse neighbourhoods and therefore attract people of all socioeconomic statuses. Our findings challenge a long-standing conjecture in human geography and highlight how urban design can both prevent and facilitate encounters among diverse individuals.