作者:未玖 来源:科学网微信公众号 发布时间:2023/12/23 21:07:17
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《自然》(20231221出版)一周论文导读

 

编译 | 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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物理学Physics

Moiré synaptic transistor with room-temperature neuromorphic functionality

具有室温神经形态功能的莫尔突触晶体管

▲ 作者:Xiaodong Yan, Zhiren Zheng, Vinod K. Sangwan, Justin H. Qian, Xueqiao Wang, Stephanie E. Liu, et al.

▲ 链接:

https://www.nature.com/articles/s41586-023-06791-1

▲ 摘要:

莫尔量子材料通过扭曲二维异质结构中增强的内部库仑相互作用,产生了奇异的电子现象。当与原子级薄材料中异常高的静电控制相结合时,莫尔异质结构有望助力下一代电子设备具有前所未有的功能。然而,尽管人们进行了广泛探索,莫尔电子现象迄今为止仅限于不切实际的低温,从而阻碍了莫尔量子材料的实际应用。

研究组报道了基于不对称双层石墨烯/六方氮化硼莫尔异质结构的低功率(20 pW)莫尔突触晶体管的实验实现和室温运行。不对称莫尔电位产生了稳健的电子棘轮态,从而实现了控制器件导电性的电荷载流子滞后、非易失性注入。

双门控莫尔异质结构中的非对称门控实现了多种生物仿真神经形态功能,如可重构的突触响应、基于时空的tempotron和Bienenstock-Cooper-Munro输入特异性适应。通过这种方式,莫尔突触晶体管实现了用于人工智能和机器学习的高效内存计算设计和边缘硬件加速器。

▲ 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.

材料科学Materials Science

Homogenizing out-of-plane cation composition in perovskite solar cells

钙钛矿太阳能电池中面外阳离子组成的均匀化

▲ 作者:Zheng Liang, Yong Zhang, Huifen Xu, Wenjing Chen, Boyuan Liu, Jiyao Zhang, et al.

▲ 链接:

https://www.nature.com/articles/s41586-023-06784-0

▲ 摘要:

FA1-xCsxPbI3钙钛矿太阳能电池中FA为甲脒,为集成高效率、持久稳定性和与大规模制造的兼容性提供了一个有吸引力的选择。尽管Cs阳离子的引入有望形成完美的钙钛矿晶格,但A位阳离子偏析引起的成分不均匀性可能会对太阳能电池的光伏性能造成不利影响。

研究组可视化了钙钛矿薄膜沿垂直方向的面外成分不均匀性,并确定了不均匀性的根本原因及其对器件的潜在影响。他们使用1-(苯磺酰基)吡咯设计了一种来均匀化钙钛矿薄膜中阳离子组成分布的策略。由此产生的p-i-n器件产生了25.2%的经认证稳态光子-电子转换效率和持久的稳定性。

▲ 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

中高熵纳米合金的三维原子结构和局部化学有序性

▲ 作者:Saman Moniri, Yao Yang, Jun Ding, Yakun Yuan, Jihan Zhou, Long Yang, et al.

▲ 链接:

https://www.nature.com/articles/s41586-023-06785-z

▲ 摘要:

中高熵合金(M/HEAs)混合了几种接近等原子组成的主要元素,代表了一种模式转换策略,用于设计冶金、催化和其他领域此前未知的材料。M/HEAs的核心假设之一是晶格畸变,已通过不同的数值和实验技术对其进行了研究。然而,确定M/HEAs中的三维(3D)晶格畸变仍颇具挑战。

此外,X射线和中子研究、原子模拟、能量色散光谱和电子衍射结果对M/HEAs中假定的随机元素混合提出了质疑,表明M/HEAs中存在局部化学有序。然而,由于能量色散光谱沿区带轴将原子柱的组成整合在一起,并且弥漫电子反射可能来自平面缺陷而非局部化学有序,因此对三维局部化学有序的直接实验观察一直很困难。

研究组利用原子电子断层扫描技术确定了M/HEA纳米粒子的3D原子位置,并定量表征了局部晶格畸变、应变张量、孪晶边界、位错核心和化学近程有序(CSRO)。结果表明,与中熵合金相比,高熵合金具有更大的局部晶格畸变和更多的不均匀应变,且该应变与CSRO有关。

研究组还在中熵合金中观察到CSRO介导孪晶形成,即孪晶发生在能量较高的CSRO区域,而能量较低的CSRO区域不会引发孪晶,这代表了首次在任何材料中将局部化学有序与结构缺陷关联起来的实验观察。他们希冀这项工作不仅可扩展人们对这类重要材料的基本理解,还将通过工程晶格畸变和局部化学有序为定制M/HEA性能提供基础。

▲ 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.

化学Chemistry

Autonomous chemical research with large language models

大型语言模型助力自主化学研究

▲ 作者:Daniil A. Boiko, Robert MacKnight, Ben Kline & Gabe Gomes

▲ 链接:

https://www.nature.com/articles/s41586-023-06792-0

▲ 摘要:

基于Transformer的大型语言模型在自然语言处理、生物学、化学和计算机编程等各个领域都取得了重大进展。

研究组展示了Coscientist的开发和性能,这是一个由GPT-4驱动的人工智能系统,通过整合互联网和文档搜索、代码执行和实验自动化等工具授权的大型语言模型,自主设计、计划和执行复杂的实验。

Coscientist展示了其在六项不同任务中加速研究的潜力,包括钯催化交叉偶联反应的成功优化,同时展示了(半)自主实验设计和执行的先进能力。该发现表明了像Coscientist这样的人工智能系统在推进研究方面的多功能性、有效性和可解释性。

▲ 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.

地球科学Earth Science

Biological carbon pump estimate based on multidecadal hydrographic data

基于多年代际水文数据的生物碳泵估算

▲ 作者:Wei-Lei Wang, Weiwei Fu, Frédéric A. C. Le Moigne, Robert T. Letscher, Yi Liu, Jin-Ming Tang, et al.

▲ 链接:

https://www.nature.com/articles/s41586-023-06772-4

▲ 摘要:

光合作用从大气中吸收二氧化碳,产生的有机碳从表层转移到中层水域。然而,目前基于观测的估计对这种生物碳泵(BCP)的强度存在分歧。地球系统模型(ESM)也显示出BCP估算值的广泛分布,表明已知碳输出途径的代表性有限。

研究组使用几十年的水文观测,通过一个逆向生物地球化学模型对BCP强度进行了自上而下的估计,该模型隐式解释了所有已知的输出途径。他们估计在73.4 m(模型透光层深度)的总有机碳(TOC)输出为15.00±1.12 Pg C/年,由于上层水柱中有机质的快速再矿化,只有三分之二的有机碳达到100 m深度。

按透光层以下的固碳时间τ划分,τ> 3个月的全球有机碳总产率为11.09±1.02 Pg C/年,τ> 1年的总产率降至8.25±0.30 Pg C/年,其中81%由下沉颗粒和垂直迁移浮游动物引起的非平流扩散垂直通量所贡献。然而,通过溶解物质和悬浮颗粒的混合和其他流体输送的有机碳输出对于满足呼吸性碳需求仍具有区域重要性。

此外,从该反演中推断出的碳封存效率的温度依赖性表明,未来全球变暖可能会加强上层海洋有机质的再循环,从而潜在削弱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.

社会学Sociology

Human mobility networks reveal increased segregation in large cities

人口流动网络表明大城市的隔离现象日益严重

▲ 作者:Hamed Nilforoshan, Wenli Looi, Emma Pierson, Blanca Villanueva, Nic Fishman, Yiling Chen, et al.

▲ 链接:

https://www.nature.com/articles/s41586-023-06757-3

▲ 摘要:

大型、密集和国际化的地区支持社会经济混合和不同个体之间的接触,是一个长期愿景。评估该假设一直很困难,因为此前对社会经济混合的衡量依赖于静态住宅数据,而不是人们在工作、休闲场所和家庭社区中的真实暴露情况。

研究组开发了一种隔离暴露的测量方法,捕捉了这些日常接触的社会经济多样性。使用手机移动数据来代表美国960万人中的16亿次真实暴露,他们测量了382个大都市统计区(MSAs)和2829个县的隔离暴露。

结果发现,在10个最大的MSA中,隔离暴露比在居民少于10万的小型MSA中高出67%。这意味着,与愿景相反,大型国际大都市地区的居民较少接触到社会经济多样化的个体;其次,大城市的社会经济隔离加剧源于其为特定社会经济群体提供了更多的差异化空间选择;第三,当一个城市的中心(如购物中心)被定位为连接不同的社区,从而吸引所有社会经济地位的人时,这种隔离加剧影响就会被抵消。

该研究结果挑战了人文地理学中一个长期存在的猜想,并强调了城市设计如何既能防止又能促进不同个体之间的互动。

▲ 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.

 

 

 

 

 


 

 
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