《自然》（20231019出版）一周論文導讀

原文地址：http://news.sciencenet.cn/htmlnews/2023/10/510693.shtm

編譯 | 未玖

Nature, 19 October 2023, VOL 622, ISSUE 7983

《自然》2023年10月19日，第622卷，7983期

物理學Physics

Coherent nanophotonic electron accelerator

相干納米光子電子加速器

▲ 作者：Tomá? Chlouba, Roy Shiloh, Stefanie Kraus, Leon Brückner, Julian Litzel & Peter Hommelhoff

▲ 鏈接：

https://www.nature.com/articles/s41586-023-06602-7

▲ 摘要：

粒子加速器是工業、科學和醫學各個領域必不可少的重要工具。通常，這些機器的占地面積從醫療應用的幾平方米開始，逐步達到大型研究中心的規模。借助光子納米結構內部激光來加速電子代表了一種微觀替代方案，其成本和尺寸有望降低幾個數量級。

盡管人們在介電激光加速研究上付出了巨大努力，包括利用光學力調控復雜的電子相空間，但迄今為止尚未顯示出有效能量增益。

研究組展示了一種可擴展的納米光子電子加速器，其相干結合了粒子加速和橫向束限制，并在僅225 nm寬的通道中加速和引導電子超過長達500 μm的距離。結果觀察到12.3 keV的最大相干能量增益，相當于增加了43%，從最初的28.4 keV增加到40.7 keV。

研究組希冀，這項工作能直接促進納米光子加速器的出現，利用最小尺寸要求的高損傷閾值介電材料，提供高達GeV/m級的高加速梯度。這些片上粒子加速器將在醫學、工業、材料研究和科學領域實現變革性應用。

▲ Abstract：

Particle accelerators are essential tools in a variety of areas of industry, science and medicine. Typically, the footprint of these machines starts at a few square metres for medical applications and reaches the size of large research centres. Acceleration of electrons with the help of laser light inside of a photonic nanostructure represents a microscopic alternative with potentially orders-of-magnitude decrease in cost and size. Despite large efforts in research on dielectric laser acceleration, including complex electron phase space control with optical forces, noteworthy energy gains have not been shown so far. Here we demonstrate a scalable nanophotonic electron accelerator that coherently combines particle acceleration and transverse beam confinement, and accelerates and guides electrons over a considerable distance of 500?μm in a just 225-nm-wide channel. We observe a maximum coherent energy gain of 12.3?keV, equalling a substantial 43% energy increase of the initial 28.4?keV to 40.7?keV. We expect this work to lead directly to the advent of nanophotonic accelerators offering high acceleration gradients up to the GeV m-1 range utilizing high-damage-threshold dielectric materials at minimal size requirements. These on-chip particle accelerators will enable transformative applications in medicine, industry, materials research and science.

Cavity-mediated thermal control of metal-to-insulator transition in 1T-TaS2

1T-TaS2中金屬-絕緣體轉變的腔介導熱調控

▲ 作者：Giacomo Jarc, Shahla Yasmin Mathengattil, Angela Montanaro, Francesca Giusti, Enrico Maria Rigoni, Rudi Sergo, et al.

▲ 鏈接：

https://www.nature.com/articles/s41586-023-06596-2

▲ 摘要：

通過弱光和強光—物質耦合，將量子材料置入光學腔中為控制物質的量子協同特性提供了一個獨特平臺。

研究組報道了關聯固態材料中金屬到絕緣體相變的可逆腔控制的實驗證據。將電荷密度波材料1T-TaS2嵌入到低溫可調諧的太赫茲腔中，揭示了通過機械調節腔鏡之間的距離及其排列，可獲得與樣品溫度較大變化相關的導電—絕緣行為之間的切換。

觀察到的較大熱變化表明了類似珀塞爾效應的情況，其中腔的光譜輪廓改變了材料與外部電磁場之間的能量交換。該發現將助力通過設計量子材料的電磁環境來控制其熱力學和宏觀輸運特性。

▲ Abstract：

Placing quantum materials into optical cavities provides a unique platform for controlling quantum cooperative properties of matter, by both weak and strong light–matter coupling. Here we report experimental evidence of reversible cavity control of a metal-to-insulator phase transition in a correlated solid-state material. We embed the charge density wave material 1T-TaS2 into cryogenic tunable terahertz cavities and show that a switch between conductive and insulating behaviours, associated with a large change in the sample temperature, is obtained by mechanically tuning the distance between the cavity mirrors and their alignment. The large thermal modification observed is indicative of a Purcell-like scenario in which the spectral profile of the cavity modifies the energy exchange between the material and the external electromagnetic field. Our findings provide opportunities for controlling the thermodynamics and macroscopic transport properties of quantum materials by engineering their electromagnetic environment.

材料科學Materials Science

Tautomeric mixture coordination enables efficient lead-free perovskite LEDs

互變異構混合物配位實現高效無鉛鈣鈦礦LED

▲ 作者：Dongyuan Han, Jie Wang, Lorenzo Agosta, Ziang Zang, Bin Zhao, Lingmei Kong, et al.

▲ 鏈接：

https://www.nature.com/articles/s41586-023-06514-6

▲ 摘要：

鹵化鉛鈣鈦礦發光二極管（PeLEDs）具備優異的光電性能。然而，鉛存在潛在毒性問題，在不影響其高外部量子效率的情況下，從性能最好的PeLEDs中去除鉛仍頗具挑戰。

研究組報道了一種通過引入氰尿酸來穩定無鉛錫鈣鈦礦TEA2SnI4（TEAI，2—噻吩乙基碘化銨）的互變異構體—混合物—配位誘導的電子局域策略。結果證明配位的一個關鍵功能是放大電子效應，即使對于那些因在鈣鈦礦表面形成氫鍵互變異構二聚體和三聚體超結構而與氰尿酸不能形成強鍵的錫原子亦是如此。

這種電子局域化弱化了安德森局域化的不利影響，提高了TEA2SnI4晶體結構的有序性。這些因素導致非輻射復合捕獲系數降低了兩個數量級，同時激子結合能提高了約兩倍。該無鉛PeLEDs具有高達20.29%的外部量子效率，其性能可與最先進的含鉛PeLEDs相媲美。

研究組希冀，這些發現將為Sn（II）鈣鈦礦的穩定性提供見解，并進一步推動無鉛鈣鈦礦的應用。

▲ Abstract：

Lead halide perovskite light-emitting diodes (PeLEDs) have demonstrated remarkable optoelectronic performance. However, there are potential toxicity issues with lead and removing lead from the best-performing PeLEDs—without compromising their high external quantum efficiencies—remains a challenge. Here we report a tautomeric-mixture-coordination-induced electron localization strategy to stabilize the lead-free tin perovskite TEA2SnI4 (TEAI is 2-thiopheneethylammonium iodide) by incorporating cyanuric acid. We demonstrate that a crucial function of the coordination is to amplify the electronic effects, even for those Sn atoms that aren’t strongly bonded with cyanuric acid owing to the formation of hydrogen-bonded tautomeric dimer and trimer superstructures on the perovskite surface. This electron localization weakens adverse effects from Anderson localization and improves ordering in the crystal structure of TEA2SnI4. These factors result in a two-orders-of-magnitude reduction in the non-radiative recombination capture coefficient and an approximately twofold enhancement in the exciton binding energy. Our lead-free PeLED has an external quantum efficiency of up to 20.29%, representing a performance comparable to that of state-of-the-art lead-containing PeLEDs. We anticipate that these findings will provide insights into the stabilization of Sn(II) perovskites and further the development of lead-free perovskite applications.

Flatband λ-Ti3O5 towards extraordinary solar steam generation

平帶λ-Ti3O5助力高效太陽能蒸汽生成

▲ 作者：Bo Yang, Zhiming Zhang, Peitao Liu, Xiankai Fu, Jiantao Wang, Yu Cao, et al.

▲ 鏈接：

https://www.nature.com/articles/s41586-023-06509-3

▲ 摘要：

太陽能蒸汽界面蒸發因其環境友好的特點，在海水淡化和污水凈化方面具有廣闊的應用前景。為了提高太陽能蒸汽生成的效率，先前的大部分努力都集中在有效地收集全太陽光譜的太陽能上。然而，調節聯合態密度對增強光熱材料太陽能吸收的重要性卻未得到重視。

研究組提出了一種通過引入平帶電子結構來大大提高聯合態密度的策略。結果表明，由于Ti-Ti二聚體在費米能級附近誘導的平帶，金屬λ-Ti3O5粉末具有96.4%的高太陽能吸收率。通過將λ-Ti3O5粉末納入具有錐形腔的三維多孔水凝膠蒸發器中，在一倍太陽光照且沒有鹽沉淀的情況下，對3.5 wt%的鹽水實現了前所未有的高蒸發率，約為6.09 kg/m2/h。

從根本上而言，暴露在λ-Ti3O5表面的Ti-Ti二聚體和U型槽結構有利于吸附水分子的解離，并有利于界面水以小分子團簇的形式蒸發。當前工作強調了Ti-Ti二聚體誘導的平帶在增強太陽能吸收以及特殊U型槽在促進水解離中的關鍵作用，這為獲得具有成本效益的太陽能—蒸汽生成提供了見解。

▲ Abstract：

Solar steam interfacial evaporation represents a promising strategy for seawater desalination and wastewater purification owing to its environmentally friendly character. To improve the solar-to-steam generation, most previous efforts have focused on effectively harvesting solar energy over the full solar spectrum. However, the importance of tuning joint densities of states in enhancing solar absorption of photothermal materials is less emphasized. Here we propose a route to greatly elevate joint densities of states by introducing a flat-band electronic structure. Our study reveals that metallic λ-Ti3O5 powders show a high solar absorptivity of 96.4% due to Ti–Ti dimer-induced flat bands around the Fermi level. By incorporating them into three-dimensional porous hydrogel-based evaporators with a conical cavity, an unprecedentedly high evaporation rate of roughly 6.09?kilograms per square metre per hour is achieved for 3.5?weight percent saline water under 1?sun of irradiation without salt precipitation. Fundamentally, the Ti–Ti dimers and U-shaped groove structure exposed on the λ-Ti3O5 surface facilitate the dissociation of adsorbed water molecules and benefit the interfacial water evaporation in the form of small clusters. The present work highlights the crucial roles of Ti–Ti dimer-induced flat bands in enchaining solar absorption and peculiar U-shaped grooves in promoting water dissociation, offering insights into access to cost-effective solar-to-steam generation.

地球科學Earth Science

Overshooting the critical threshold for the Greenland ice sheet

格陵蘭冰蓋融化超過臨界閾值

▲ 作者：Nils Bochow, Anna Poltronieri, Alexander Robinson, Marisa Montoya, Martin Rypdal & Niklas Boers

▲ 鏈接：

https://www.nature.com/articles/s41586-023-06503-9

▲ 摘要：

人為全球變暖導致格陵蘭冰蓋（GrIS）融化，對全球海平面上升（SLR）構成嚴重威脅。模型和古氣候證據表明，北極迅速升高的溫度可觸發GrIS的正反饋機制，導致自身持續融化，GrIS已被證明可保持幾種穩定狀態。當全球平均溫度（GMT）超過特定閾值時，預計會發生臨界轉變，在穩定狀態之間存在顯著滯后。

研究組使用兩個獨立的冰蓋模型來研究具有不同峰值溫度和收斂溫度的不同超調情景對大范圍變暖和隨后變冷速率的影響。結果表明，最大GMT和超過給定GMT目標的時間跨度是決定GrIS穩定性的關鍵。

當閾值GMT比工業化前水平高出1.7℃至2.3℃時，或導致冰蓋急劇消失。如果GMT隨后在幾個世紀內降低到比工業化前水平高1.5℃以下，即使最高GMT比工業化前水平高6℃及以上，GrIS的損失也可以大大減輕。

但研究結果也表明，即使暫時超過溫度閾值，尚未過渡到新冰蓋狀態時，SLR仍會達到幾米的峰值。

▲ Abstract：

Melting of the Greenland ice sheet (GrIS) in response to anthropogenic global warming poses a severe threat in terms of global sea-level rise (SLR). Modelling and palaeoclimate evidence suggest that rapidly increasing temperatures in the Arctic can trigger positive feedback mechanisms for the GrIS, leading to self-sustained melting, and the GrIS has been shown to permit several stable states. Critical transitions are expected when the global mean temperature (GMT) crosses specific thresholds, with substantial hysteresis between the stable states. Here we use two independent ice-sheet models to investigate the impact of different overshoot scenarios with varying peak and convergence temperatures for a broad range of warming and subsequent cooling rates. Our results show that the maximum GMT and the time span of overshooting given GMT targets are critical in determining GrIS stability. We find a threshold GMT between 1.7?℃ and 2.3?℃ above preindustrial levels for an abrupt ice-sheet loss. GrIS loss can be substantially mitigated, even for maximum GMTs of 6?℃ or more above preindustrial levels, if the GMT is subsequently reduced to less than 1.5?℃ above preindustrial levels within a few centuries. However, our results also show that even temporarily overshooting the temperature threshold, without a transition to a new ice-sheet state, still leads to a peak in SLR of up to several metres.

Tropical Atlantic multidecadal variability is dominated by external forcing

熱帶大西洋多年代際變化主要由外部強迫主導

▲ 作者：Chengfei He, Amy C. Clement, Sydney M. Kramer, Mark A. Cane, Jeremy M. Klavans, Tyler M. Fenske, et al.

▲ 鏈接：

https://www.nature.com/articles/s41586-023-06489-4

▲ 摘要：

熱帶大西洋氣候的特征表現為大西洋海表溫度（SSTs）、薩赫勒降雨量和颶風活動顯著且相關的多年代際變化。由于模型和觀測的不確定性，這些系統之間物理關系的起源仍存在爭議。

研究組表明，自1950年以來，熱帶大西洋SST的跨赤道梯度主要由與人為排放和火山氣溶膠相關的輻射擾動驅動，這是大西洋颶風形成和薩赫勒降雨量的關鍵決定因素。這種關系在大量CMIP6地球系統模型中很模糊，因為這些模型高估了1950年左右以來北半球相對于南半球的長期變暖趨勢，以及大氣環流和降雨量的相關變化。

當消除高估趨勢后，SST與大西洋颶風形成和薩赫勒降雨量之間的相關性表現出對輻射強迫的響應，特別是自1950年以來，當時人為氣溶膠強迫一直很高。研究結果表明，熱帶大西洋SST梯度與整個北大西洋的SST相比，更能決定熱帶影響，因為該梯度通過局部大氣環流與熱帶影響的物理聯系更緊密。

該結果強調，大西洋颶風活動和薩赫勒降雨量變化可以通過人為排放和火山活動驅動的輻射強迫來預測，但更可靠的預測受到未來氣候強迫的信噪比悖論和不確定性的限制。

▲ Abstract：