Nature, 15 September 2022, VOL 609, ISSUE 7927
《自然》2022年9月15日，第609卷，7927期
物理学Physics
Femtosecond laser writing of lithium niobate ferroelectric nanodomains
飞秒激光写入铌酸锂铁电纳米畴
▲ 作者：Xiaoyi Xu, Tianxin Wang, Pengcheng Chen, Chao Zhou, Jianan Ma, Dunzhao Wei, Huijun Wang, Ben Niu, Xinyuan Fang, Di Wu, Shining Zhu, Min Gu, Min Xiao & Yong Zhang
▲ 链接：https://www.nature.com/articles/s41586-022-05042-z
▲ 摘要：铌酸锂（LiNbO3）是一种很有前途的光通信和量子光子芯片材料。作者展示了一种非互易的近红外激光书写技术，用于在LiNbO3中具有纳米级分辨率的可重构三维铁电畴工程。
提出的方法是基于激光诱导电场，根据激光写入的方向，可以写入或擦除晶体中的畴结构。该方法为LiNbO3等透明铁电晶体的可控纳米畴工程提供了一条途径，在高效混频、高频声谐振器和大容量非易失性铁电存储器等方面具有潜在的应用价值。
▲ Abstract：Lithium niobate (LiNbO3) is viewed as a promising material for optical communications and quantum photonic chips. Here we demonstrate a non-reciprocal near-infrared laser-writing technique for reconfigurable three-dimensional ferroelectric domain engineering in LiNbO3 with nanoscale resolution. The proposed method is based on a laser-induced electric field that can either write or erase domain structures in the crystal, depending on the laser-writing direction. This approach offers a pathway for controllable nanoscale domain engineering in LiNbO3 and other transparent ferroelectric crystals, which has potential applications in high-efficiency frequency mixing, high-frequency acoustic resonators and high-capacity non-volatile ferroelectric memory.
Attosecond spectroscopy of size-resolved water clusters
大小分辨水团簇的阿秒光谱
▲ 作者：Xiaochun Gong, Saijoscha Heck, Denis Jelovina, Conaill Perry, Kristina Zinchenko, Robert Lucchese & Hans Jakob Wrner
▲ 链接：https://www.nature.com/articles/s41586-022-05039-8
▲ 摘要：水中电子动力学对许多现象具有基础性的重要性，但其实时研究面临着许多概念和方法上的挑战。作者介绍了阿秒大小分辨聚类光谱，建立对水中阿秒电子动力学的分子水平的理解。他们测量了单个水分子的加入对水簇光离时延的影响，结果发现对于含有4到5个分子的团簇，延迟持续增加，而对于更大的团簇，延迟变化不大。
研究者证明了这些延迟与所产生的电子空穴的空间扩展成正比，电子空穴首先随着团簇的大小而增加，然后通过大团簇和大体积液态水的结构紊乱的出现而部分定位。
这些结果表明光离延迟对电子空穴离域的敏感性是未知的，也表明电子结构和阿秒光离动力学之间的直接联系。该结果为研究电子空穴离域及其阿秒动力学提供了新的视角。
▲ Abstract：Electron dynamics in water are of fundamental importance for a broad range of phenomena, but their real-time study faces numerous conceptual and methodological challenges. Here we introduce attosecond size-resolved cluster spectroscopy and build up a molecular-level understanding of the attosecond electron dynamics in water. We measure the effect that the addition of single water molecules has on the photoionization time delays of water clusters. We find a continuous increase of the delay for clusters containing up to four to five molecules and little change towards larger clusters. We show that these delays are proportional to the spatial extension of the created electron hole, which first increases with cluster size and then partially localizes through the onset of structural disorder that is characteristic of large clusters and bulk liquid water. These results indicate a previously unknown sensitivity of photoionization delays to electron-hole delocalization and indicate a direct link between electronic structure and attosecond photoionization dynamics. Our results offer new perspectives for studying electron-hole delocalization and its attosecond dynamics.
Extended Bose–Hubbard model with dipolar excitons
带有偶极激子的扩展玻色-哈伯德模型
▲ 作者：C. Lagoin, U. Bhattacharya, T. Grass, R. W. Chhajlany, T. Salamon, K. Baldwin, L. Pfeiffer, M. Lewenstein, M. Holzmann & F. Dubin
▲ 链接：https://www.nature.com/articles/s41586-022-05123-z
▲ 摘要：哈伯德模型是凝聚态物理最著名的理论框架之一。它描述了限制在晶格势中的相互作用量子粒子的强相关相。对于玻色子，哈伯德哈密顿量已经被深入研究了近距离现场相互作用。
然而，在实验上，获得更远距离的耦合仍然难以捉摸。这标志着向扩展的玻色-哈伯德哈密顿量的前沿，它使得在分数点阵填充中隔离有序相成为可能。作者通过限制半导体偶极激子，在一个人工的二维方形晶格实现这个哈密顿量。
最强的偶极排斥力在最近邻的晶格位之间使半填充状态稳定在绝缘状态。扩展玻色-哈伯德模型的这一特征显示了棋盘格空间顺序的理论特征。因此，这项研究强调了偶极激子在具有可编程几何结构和超过100个位点的晶格中，使具有强站外相互作用的类玻色子阵列的受控实现成为可能。
▲ Abstract：
The Hubbard model constitutes one of the most celebrated theoretical frameworks of condensed-matter physics. It describes strongly correlated phases of interacting quantum particles confined in lattice potentials. For bosons, the Hubbard Hamiltonian has been deeply scrutinized for short-range on-site interactions. However, accessing longer-range couplings has remained elusive experimentally. This marks the frontier towards the extended Bose–Hubbard Hamiltonian, which enables insulating ordered phases at fractional lattice fillings. Here we implement this Hamiltonian by confining semiconductor dipolar excitons in an artificial two-dimensional square lattice. Strong dipolar repulsions between nearest-neighbour lattice sites then stabilize an insulating state at half filling. This characteristic feature of the extended Bose–Hubbard model exhibits the signatures theoretically expected for a chequerboard spatial order. Our work thus highlights that dipolar excitons enable controlled implementations of boson-like arrays with strong off-site interactions, in lattices with programmable geometries and more than 100 sites.
化学Chemistry
The first-principles phase diagram of monolayer nanoconfined water
单层纳米承压水的第一性原理相图
▲ 作者：Venkat Kapil, Christoph Schran, Andrea Zen, Ji Chen, Chris J. Pickard & Angelos Michaelides
▲ 链接：https://www.nature.com/articles/s41586-022-05036-x
▲ 摘要：纳米级空腔中的水无处不在，对地质学和生物学的日常现象至关重要。然而，纳米级水的性质可以与体积水的性质有本质上的不同。
作者结合了一系列的计算方法，实现对石墨烯类通道内单层水的第一性原理级研究。他们发现单分子层水表现出惊人的丰富和多样化的相行为，对温度和作用在纳米通道内的范德华压力高度敏感。
除了熔化温度随压力非单调变化超过400开尔文的多个分子相外，他们还预测了一个六相，它是介于固体和液体之间的中间物，以及一个具有高导电性的超离子相，其导电性超过电池材料。值得注意的是，这表明纳米约束可能是在容易接近的条件下实现超声子行为的有希望的途径。
▲ Abstract： Water in nanoscale cavities is ubiquitous and of central importance to everyday phenomena in geology and biology. However, the properties of nanoscale water can be substantially different from those of bulk water. Here we combine a range of computational approaches to enable a first-principles-level investigation of a single layer of water within a graphene-like channel. We find that monolayer water exhibits surprisingly rich and diverse phase behaviour that is highly sensitive to temperature and the van der Waals pressure acting within the nanochannel. In addition to multiple molecular phases with melting temperatures varying non-monotonically by more than 400 kelvins with pressure, we predict a hexatic phase, which is an intermediate between a solid and a liquid, and a superionic phase with a high electrical conductivity exceeding that of battery materials. Notably, this suggests that nanoconfinement could be a promising route towards superionic behaviour under easily accessible conditions.
气候学Climate
A year-round satellite sea-ice thickness record from CryoSat-2
CryoSat-2的全年卫星海冰厚度记录
▲ 作者：Jack C. Landy, Geoffrey J. Dawson, Michel Tsamados, Mitchell Bushuk, Julienne C. Stroeve, Stephen E. L. Howell, Thomas Krumpen, David G. Babb, Alexander S. Komarov, Harry D. B. S. Heorton, H. Jakob Belter & Yevgeny Aksenov
▲ 链接：https://www.nature.com/articles/s41586-022-05058-5
▲ 摘要：
随着气候变暖，北极海冰正在以至少千年来前所未有的速度减少。随着冰原的消融引起北极地区商业利益的增加，它变得更加多变和易移动，这增加了海上用户的安全风险。
但5月至9月这一关键的融冰期，目前无法进行海冰厚度的卫星观测。而在这一时期，由于处理测高数据面临重大挑战，卫星观测对季节性预测等应用最有价值。
作者使用深度学习和欧洲航天局建造的极地测高卫星CryoSat-2的雷达高度计响应的数值模拟来克服这些挑战，并为北极融化期生成泛北极海冰厚度数据集。
CryoSat-2观测捕获了由独立传感器记录的冰融化速率的空间和时间模式，并与泛北极冰海洋模拟和同化系统再分析所模拟的海冰体积的时间序列相匹配。
2011 - 2020年5月融化季开始时，北极海冰厚度为1.87±0.10 米；8月融化季结束时，海冰厚度为0.82±0.11 米。这一全年的海冰厚度记录为理解北极气候在不同时间尺度上的反馈提供了机会。
▲ Abstract： Arctic sea ice is diminishing with climate warming at a rate unmatched for at least 1,000 years. As the receding ice pack raises commercial interest in the Arctic, it has become more variable and mobile, which increases safety risks to maritime users5. Satellite observations of sea-ice thickness are currently unavailable during the crucial melt period from May to September, when they would be most valuable for applications such as seasonal forecasting, owing to major challenges in the processing of altimetry data. Here we use deep learning and numerical simulations of the CryoSat-2 radar altimeter response to overcome these challenges and generate a pan-Arctic sea-ice thickness dataset for the Arctic melt period. CryoSat-2 observations capture the spatial and the temporal patterns of ice melting rates recorded by independent sensors and match the time series of sea-ice volume modelled by the Pan-Arctic Ice Ocean Modelling and Assimilation System reanalysis. Between 2011 and 2020, Arctic sea-ice thickness was 1.87±0.10m at the start of the melting season in May and 0.82±0.11m by the end of the melting season in August. Our year-round sea-ice thickness record unlocks opportunities for understanding Arctic climate feedbacks on different timescales.
地质学Geology
Rapid shifting of a deep magmatic source at Fagradalsfjall volcano, Iceland
冰岛法格拉达尔火山深部岩浆源的快速移动
▲ 作者：Sæmundur A. Halldórsson, Edward W. Marshall, Alberto Caracciolo et al.
▲ 链接：
https://www.nature.com/articles/s41586-022-04981-x
▲ 摘要：冰岛裂谷事件揭示了集中的地壳岩浆储层和侧向岩浆运移的作用，以及洋中脊岩浆活动的重要特征。这种浅层地壳对岩浆的加工的结果是，在最上地幔和最下地壳中，重叠印出了追溯熔体起源、演化和迁移的特征。作者通过对冰岛雷克简斯半岛2021年格拉达尔火山喷发的综合岩石学和地球化学研究，对该区域发生的过程提出了独特的见解。
对喷发前50天喷发的玄武岩的地球化学分析，结合相关气体排放，揭示了其直接来源近莫霍区岩浆储存带。地球化学指标表示不同的地幔成分和熔融条件，其变化速度之快是全球单个玄武岩喷发所无法比拟的。
最初，喷发的熔岩主要由来自最浅层地幔的熔体构成，但在随后的三周内，岩浆越来越多地由更深处的岩浆构成。这种喷发成分异常迅速的趋势提供了前所未有的岩浆混合的时间记录，过滤了地幔信号，与含有107-108立方米玄武岩浆的近莫霍熔融透镜的处理一致。通过对这一关键岩浆处理区的近实时调查，可以对玄武岩岩浆系统的时间尺度和运作模式有新的认识。
▲ Abstract：
Recent Icelandic rifting events have illuminated the roles of centralized crustal magma reservoirs and lateral magma transport, important characteristics of mid-ocean ridge magmatism. A consequence of such shallow crustal processing of magmas is the overprinting of signatures that trace the origin, evolution and transport of melts in the uppermost mantle and lowermost crust. Here we present unique insights into processes occurring in this zone from integrated petrologic and geochemical studies of the 2021 Fagradalsfjall eruption on the Reykjanes Peninsula in Iceland. Geochemical analyses of basalts erupted during the first 50 days of the eruption, combined with associated gas emissions, reveal direct sourcing from a near-Moho magma storage zone. Geochemical proxies, which signify different mantle compositions and melting conditions, changed at a rate unparalleled for individual basaltic eruptions globally. Initially, the erupted lava was dominated by melts sourced from the shallowest mantle but over the following three weeks became increasingly dominated by magmas generated at a greater depth. This exceptionally rapid trend in erupted compositions provides an unprecedented temporal record of magma mixing that filters the mantle signal, consistent with processing in near-Moho melt lenses containing 107-108 m3 of basaltic magma. Exposing previously inaccessible parts of this key magma processing zone to near-real-time investigations provides new insights into the timescales and operational mode of basaltic magma systems.
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