編譯 | 馮維維
Nature, 15 September 2022, VOL 609, ISSUE 7927
《自然》2022年9月15日，第609卷，7927期
物理學Physics
Femtosecond laser writing of Lithium niobate ferroelectric nanodomains
飛秒激光寫入鈮酸鋰鐵電納米疇
▲ 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
▲ 鏈接：
https://www.nature.com/articles/s41586-022-05042-z
▲ 摘要：
鈮酸鋰（LiNbO3）是一種很有前途的光通信和量子光子芯片材料。作者展示了一種非互易的近紅外激光書寫技術，用於在LiNbO3中具有納米級分辨率的可重構三維鐵電疇工程。
提出的方法是基於激光誘導電場，根據激光寫入的方向，可以寫入或擦除晶體中的疇結構。該方法為LiNbO3等透明鐵電晶體的可控納米疇工程提供了一條途徑，在高效混頻、高頻聲諧振器和大容量非易失性鐵電存儲器等方面具有潛在的應用價值。
▲ 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
大小分辨水團簇的阿秒光譜
▲ 作者：Xiaochun Gong, Saijoscha Heck, Denis Jelovina, Conaill Perry, Kristina Zinchenko, Robert Lucchese & Hans Jakob Wrner
▲ 鏈接：
https://www.nature.com/articles/s41586-022-05039-8
▲ 摘要：
水中電子動力學對許多現象具有基礎性的重要性，但其實時研究面臨著許多概念和方法上的挑戰。作者介紹了阿秒大小分辨聚類光譜，建立對水中阿秒電子動力學的分子水平的理解。他們測量了單個水分子的加入對水簇光離時延的影響，結果發現對於含有4到5個分子的團簇，延遲持續增加，而對於更大的團簇，延遲變化不大。
研究者證明了這些延遲與所產生的電子空穴的空間擴展成正比，電子空穴首先隨着團簇的大小而增加，然後通過大團簇和大體積液態水的結構紊亂的出現而部分定位。
這些結果表明光離延遲對電子空穴離域的敏感性是未知的，也表明電子結構和阿秒光離動力學之間的直接聯繫。該結果為研究電子空穴離域及其阿秒動力學提供了新的視角。
▲ 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
帶有偶極激子的擴展玻色-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
▲ 鏈接：
https://www.nature.com/articles/s41586-022-05123-z
▲ 摘要：
哈伯德模型是凝聚態物理最著名的理論框架之一。它描述了限制在晶格勢中的相互作用量子粒子的強相關相。對於玻色子，哈伯德哈密頓量已經被深入研究了近距離現場相互作用。
然而，在實驗上，獲得更遠距離的耦合仍然難以捉摸。這標誌着向擴展的玻色-哈伯德哈密頓量的前沿，它使得在分數點陣填充中隔離有序相成為可能。作者通過限制半導體偶極激子，在一個人工的二維方形晶格實現這個哈密頓量。
最強的偶極排斥力在最近鄰的晶格位之間使半填充狀態穩定在絕緣狀態。擴展玻色-哈伯德模型的這一特徵顯示了棋盤格空間順序的理論特徵。因此，這項研究強調了偶極激子在具有可編程幾何結構和超過100個位點的晶格中，使具有強站外相互作用的類玻色子陣列的受控實現成為可能。
▲ 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.
化學Chemistry
The first-principles phase diagram of monolayer nanoconfined water
單層納米承壓水的第一性原理相圖
▲ 作者：Venkat Kapil, Christoph Schran, Andrea Zen, Ji Chen, Chris J. Pickard & Angelos Michaelides
▲ 鏈接：
https://www.nature.com/articles/s41586-022-05036-x
▲ 摘要：
納米級空腔中的水無處不在，對地質學和生物學的日常現象至關重要。然而，納米級水的性質可以與體積水的性質有本質上的不同。
作者結合了一系列的計算方法，實現對石墨烯類通道內單層水的第一性原理級研究。他們發現單分子層水表現出驚人的豐富和多樣化的相行為，對溫度和作用在納米通道內的范德華壓力高度敏感。
除了熔化溫度隨壓力非單調變化超過400開爾文的多個分子相外，他們還預測了一個六相，它是介於固體和液體之間的中間物，以及一個具有高導電性的超離子相，其導電性超過電池材料。值得注意的是，這表明納米約束可能是在容易接近的條件下實現超聲子行為的有希望的途徑。
▲ 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.
氣候學Climate
A year-round satellite sea-ice thickness record from CryoSat-2
CryoSat-2的全年衛星海冰厚度記錄
▲ 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
▲ 鏈接：
https://www.nature.com/articles/s41586-022-05058-5
▲ 摘要：
隨着氣候變暖，北極海冰正在以至少千年來前所未有的速度減少。隨着冰原的消融引起北極地區商業利益的增加，它變得更加多變和易移動，這增加了海上用戶的安全風險。
但5月至9月這一關鍵的融冰期，目前無法進行海冰厚度的衛星觀測。而在這一時期，由於處理測高數據面臨重大挑戰，衛星觀測對季節性預測等應用最有價值。
作者使用深度學習和歐洲航天局建造的極地測高衛星CryoSat-2的雷達高度計響應的數值模擬來克服這些挑戰，並為北極融化期生成泛北極海冰厚度數據集。
CryoSat-2觀測捕獲了由獨立傳感器記錄的冰融化速率的空間和時間模式，並與泛北極冰海洋模擬和同化系統再分析所模擬的海冰體積的時間序列相匹配。
2011 - 2020年5月融化季開始時，北極海冰厚度為1.87±0.10 米；8月融化季結束時，海冰厚度為0.82±0.11 米。這一全年的海冰厚度記錄為理解北極氣候在不同時間尺度上的反饋提供了機會。
▲ 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.
地質學Geology
Rapid shifting of a deep magmatic source at Fagradalsfjall volcano, Iceland
冰島法格拉達爾火山深部岩漿源的快速移動
▲ 作者：Sæmundur A. Halldórsson, Edward W. Marshall, Alberto Caracciolo et al.
▲ 鏈接：
https://www.nature.com/articles/s41586-022-04981-x
▲ 摘要：
冰島裂谷事件揭示了集中的地殼岩漿儲層和側向岩漿運移的作用，以及洋中脊岩漿活動的重要特徵。這種淺層地殼對岩漿的加工的結果是，在最上地幔和最下地殼中，重疊印出了追溯熔體起源、演化和遷移的特徵。作者通過對冰島雷克簡斯半島2021年格拉達爾火山噴發的綜合岩石學和地球化學研究，對該區域發生的過程提出了獨特的見解。
對噴發前50天噴發的玄武岩的地球化學分析，結合相關氣體排放，揭示了其直接來源近莫霍區岩漿儲存帶。地球化學指標表示不同的地幔成分和熔融條件，其變化速度之快是全球單個玄武岩噴發所無法比擬的。
最初，噴發的熔岩主要由來自最淺層地幔的熔體構成，但在隨後的三周內，岩漿越來越多地由更深處的岩漿構成。這種噴發成分異常迅速的趨勢提供了前所未有的岩漿混合的時間記錄，過濾了地幔信號，與含有107-108立方米玄武岩漿的近莫霍熔融透鏡的處理一致。通過對這一關鍵岩漿處理區的近實時調查，可以對玄武岩岩漿系統的時間尺度和運作模式有新的認識。
▲ 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.
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-