赵帅在《自然》上发表论文

编译 | 李言

Nature , 29 April 2021, Volume 592 Issue 7856

《自然》 2021年4月29日，第592卷，7856期

天文学 Astronomy

X-ray quasi-periodic eruptions from two previously quiescent galaxies

两个之前静止的星系的X射线准周期性爆发

作者：R. Arcodia, A. Merloni, K. Nandra, J. Buchner, M. Salvato, et al.

链接：

摘要

准周期性爆发（QPEs）是每隔几小时发生一次的x射线辐射的高振幅爆发，通常起源于星系核的中心特大质量黑洞附近。在此，我们报告了对另外两个星系的QPEs的观测，这是通过对X射线天空的一半进行系统的盲搜获得的。

这些星系的光谱没有显示出黑洞活动的特征，这表明活跃星系核的一个典型的预先存在的吸积流并不需要触发这些事件。事实上，这里报告的QPEs的周期、振幅和剖面与当前的模型不一致，这些模型在吸积盘中引发了辐射压力驱动的不稳定性。

相反，QPEs可能是由一个轨道上的致密物体驱动的。此外，它们的观测性质要求次级天体的质量要比主体的质量小得多，未来的X射线观测可能会限制由于轨道演化而导致的周期变化。

Abstract

Quasi-periodic eruptions (QPEs) are very-high-amplitude bursts of X-ray radiation recurring every few hours and originating near the central supermassive black holes of galactic nuclei. Here we report observations of QPEs in two further galaxies, obtained with a blind and systematic search of half of the X-ray sky. The optical spectra of these galaxies show no signature of black hole activity, indicating that a pre-existing accretion flow that is typical of active galactic nuclei is not required to trigger these events. Indeed, the periods, amplitudes and profiles of the QPEs reported here are inconsistent with current models that invoke radiation-pressure-driven instabilities in the accretion disk. Instead, QPEs might be driven by an orbiting compact object. Furthermore, their observed properties require the mass of the secondary object to be much smaller than that of the main body, and future X-ray observations may constrain possible changes in their period owing to orbital evolution.

化学 Chemistry

Transition from an atomic to a molecular Bose–Einstein condensate

从原子到分子的玻色-爱因斯坦凝聚物的跃迁

作者：Zhendong Zhang, Liangchao Chen, Kai-Xuan Yao & Cheng Chin

链接：

摘要

分子量子气体（即超冷高密度分子气体）有许多潜在的应用方式，包括化学反应的量子控制、精密测量、量子模拟和量子信息处理。在此，我们报告在g波费希巴赫共振附近的原子凝聚物中，通过诱导对相互作用制备旋转分子的二维玻色-爱因斯坦凝聚物（BECs）。

陷阱的几何形状和分子的低温有助于减少非弹性损失，确保热平衡。从状态方程测量，我们确定分子散射长度为+ 220( 30)玻尔半径（95%置信区间）。我们还研究了强耦合条件下的解对动力学，发现在费什巴赫共振附近的动力学时间尺度符合统一极限。

Abstract

Molecular quantum gases (that is, ultracold and dense molecular gases) have many potential applications, including quantum control of chemical reactions, precision measurements, quantum simulation and quantum information processing. Here we report the preparation of two-dimensional Bose–Einstein condensates (BECs) of spinning molecules by inducing pairing interactions in an atomic condensate near a g-wave Feshbach resonance. The trap geometry and the low temperature of the molecules help to reduce inelastic loss, ensuring thermal equilibrium. From the equation-of-state measurement, we determine the molecular scattering length to be + 220( 30) Bohr radii (95% confidence interval). We also investigate the unpairing dynamics in the strong coupling regime and find that near the Feshbach resonance the dynamical timescale is consistent with the unitarity limit.

Direct observation of chemical short-range order in a medium-entropy alloy

对中熵合金中化学短程顺序的直接观察

作者：Xuefei Chen, Qi Wang, Zhiying Cheng, Mingliu Zhu, Hao Zhou, Ping Jiang, et al.

链接：

摘要

在此，我们发现使用适当的区域轴、微/纳米束衍射以及通过透射电子显微镜的原子分辨率成像和化学映射，可以明确地发现在面心立方VCoNi浓缩溶液中的CSRO。

我们的互补工具套件提供了关于CSRO的程度/程度、原子填充配置和化学物种对邻近晶格面/位的优先占用的具体信息。对最近原子壳层上的CSRO阶数参数和对相关性的建模表明，CSRO源自最近邻偏好，朝向不同的（V-Co和V-Ni）对，并避免了V-V对。

我们的发现为鉴定浓溶液合金中的CSRO提供了一种方法。我们还使用原子应变映射来展示由CSRO增强的位错相互作用，阐明这些CSRO对变形时塑性机制和力学性能的影响。

Abstract

Here we discover that, using an appropriate zone axis, micro/nanobeam diffraction, together with atomic-resolution imaging and chemical mapping via transmission electron microscopy, can explicitly reveal CSRO in a face-centred-cubic VCoNi concentrated solution. Our complementary suite of tools provides concrete information about the degree/extent of CSRO, atomic packing configuration and preferential occupancy of neighbouring lattice planes/sites by chemical species. Modelling of the CSRO order parameters and pair correlations over the nearest atomic shells indicates that the CSRO originates from the nearest-neighbour preference towards unlike (V Co and V Ni) pairs and avoidance of V V pairs. Our findings offer a way of identifying CSRO in concentrated solution alloys. We also use atomic strain mapping to demonstrate the dislocation interactions enhanced by the CSROs, clarifying the effects of these CSROs on plasticity mechanisms and mechanical properties upon deformation.

Direct assessment of the acidity of inpidual surface hydroxyls

直接评估单个表面羟基的酸度

作者：Margareta Wagner, Bernd Meyer, Martin Setvin, Michael Schmid & Ulrike Diebold

链接：

摘要

矿物表面的酸度是通过半经验概念来估计的，如键序价和，并越来越多地采用第一性原理分子动力学模拟。目前，这种预测还无法通过实验测量得到验证，比如在整个表面上或者在某些情况下的单个晶体刻面的零电荷点。

在此，我们评估了In2O3(111)上单个羟基的酸性。In2O3(111)是一种具有四种不同表面氧原子的模型氧化物。我们用非接触原子力显微镜的尖端探测了它们的氢键强度，发现了与密度泛函理论计算的定量一致。

通过将结果与气相分子的质子亲合能联系起来，我们以原子的精度确定了In2O3不同表面位点的质子亲合能。

Abstract

For mineral surfaces, the acidity is estimated by semi-empirical concepts, such as bond-order valence sums, and increasingly modelled with first-principles molecular dynamics simulations. At present, such predictions cannot be tested—experimental measures, such as the point of zero charge, integrate over the whole surface or, in some cases, inpidual crystal facets. Here we assess the acidity of inpidual hydroxyl groups on In2O3(111)—a model oxide with four different types of surface oxygen atom. We probe the strength of their hydrogen bonds with the tip of a non-contact atomic force microscope and find quantitative agreement with density functional theory calculations. By relating the results to known proton affinities of gas-phase molecules, we determine the proton affinity of the different surface sites of In2O3 with atomic precision.

地球科学 Geoscience

Accelerated global glacier mass loss in the early twenty-first century

21世纪初全球冰川数量的加速流失

作者：Romain Hugonnet, Robert McNabb, Etienne Berthier, et al

链接：

摘要

在此，我们揭示了冰川质量在21世纪早期加速流失的模式。我们的研究显示，2000-2019年期间，冰川每年损失267 160亿吨，相当于观测到的海平面上升的21 3%。

我们发现，质量损失的加速度为每年每10年48 160亿吨，这解释了观测到的6%至19%海平面上升的加速度。特别是，冰盖外围的冰川变薄的速度在过去20年里翻了一番。目前，与格陵兰岛或南极冰原分别相比，冰川的质量损失更大，速度相近或更快。

通过揭示许多地区的质量变化模式，我们发现冰川的对比波动与降水和温度的年代际变化一致。包括北大西洋异常的质量减少，美国西北部冰川的异常强烈减少，以及喀喇昆仑山脉异常增多的明显终结。

Abstract

Here we reveal the accelerated, albeit contrasting, patterns of glacier mass loss during the early twenty-first century. We show that during 2000–2019, glaciers lost a mass of 267 16 gigatonnes per year, equivalent to 21 3 per cent of the observed sea-level rise. We identify a mass loss acceleration of 48 16 gigatonnes per year per decade, explaining 6 to 19 per cent of the observed acceleration of sea-level rise. Particularly, thinning rates of glaciers outside ice sheet peripheries doubled over the past two decades. Glaciers currently lose more mass, and at similar or larger acceleration rates, than the Greenland or Antarctic ice sheets taken separately. By uncovering the patterns of mass change in many regions, we find contrasting glacier fluctuations that agree with the decadal variability in precipitation and temperature. These include a North Atlantic anomaly of decelerated mass loss, a strongly accelerated loss from northwestern American glaciers, and the apparent end of the Karakoram anomaly of mass gain.

Plume-driven recratonization of deep continental lithospheric mantle

地幔柱驱动岩石圈地幔的克拉通再生

作者：Jingao Liu, D. Graham Pearson, Lawrence Hongliang Wang, et al.

链接：

摘要

克拉通的地幔根被认为是地球大陆长期稳定的特征，但也有证据表明它们在最近和更遥远的过去发生了分裂。在此，我们研究了加拿大北极克拉通岩石圈的地幔橄榄岩携带的地幔包体和地震学，其中包括12.7亿年前受麦肯齐地幔柱事件影响的地区。

我们论证了地幔柱上升流对奴隶克拉通北部约200公里厚克拉通岩石圈地幔的破坏和再活化的重要作用。通过数值模拟，我们展示了在两个厚克拉通地块之间的岩石圈变薄的区域中，麦肯齐地幔柱事件产生的新的熔融地幔残余体是如何被捕获的。

我们的结果确定在山根被破坏后，克拉通能够愈合并恢复到原来的厚度。

Abstract

The mantle roots of cratons are renowned as being long-lived, stable features of Earth’s continents, but there is also evidence of their disruption in the recent and more distant past. Here we study kimberlite-borne mantle xenoliths and seismology across a transect of the cratonic lithosphere of Arctic Canada, which includes a region affected by the Mackenzie plume event 1.27 billion years ago. We demonstrate the important role of plume upwelling in the destruction and recratonization of roughly 200-kilometre-thick cratonic lithospheric mantle in the northern portion of the Slave craton. Using numerical modelling, we show how new, buoyant melt residues produced by the Mackenzie plume event are captured in a region of thinned lithosphere between two thick cratonic blocks. Our results identify a process by which cratons heal and return to their original lithospheric thickness after substantial disruption of their roots.

编译 | 李言

Nature , 8 April 2021, Volume 592 Issue 7853

《自然》 2021年4月8日，第592卷，7853期

天文学 Astronomy

Five carbon- and nitrogen-bearing species in a hot giant planet’s atmosphere

在炎热巨型行星大气层中的五种含碳和氮的物质

作者：Paolo Giacobbe, Matteo Brogi, Siddharth Gandhi, Patricio E. Cubillos, et al.

链接：

摘要

先前对热木星的观测表明，它们在其主星前面经过时大气层中经常存在水蒸气和一氧化碳；这已经通过在通常的化学平衡假设下根据太阳的比例组成进行了研究。

氰化氢和这两种分子都在HD 209458b的大气中被发现。HD 209458b是一个被充分研究过的热木星（平衡温度在1500 k左右），曾经检测出氨，但随后被否认。

在此，我们报告HD 209458b的观察结果，显示存在水、一氧化碳、氰化氢、甲烷、氨和乙炔，每个分子5.3到9.9个标准偏差。辐射和化学平衡的大气模型表明，探测到的物质具有富碳化学成分，碳氧比接近或大于1，高于太阳的值（0.55）。

根据现有的关于大气化学与行星形成和迁移情景的模型，这可能表明HD 209458b在远离目前位置的地方形成，随后向内迁移。

Abstract

Previous observations of hot Jupiters as they transit in front of their host stars have revealed the frequent presence of water vapour and carbon monoxide in their atmospheres; this has been studied in terms of scaled solar composition under the usual assumption of chemical equilibrium. Both molecules as well as hydrogen cyanide were found in the atmosphere of HD 209458b, a well studied hot Jupiter (with equilibrium temperature around 1,500 kelvin), whereas ammonia was tentatively detected there and subsequently refuted. Here we report observations of HD 209458b that indicate the presence of water ( H2 O), carbon monoxide (CO), hydrogen cyanide (HCN), methane (C H4 ), ammonia (N H3 ) and acetylene ( C2H2 ), with statistical significance of 5.3 to 9.9 standard deviations per molecule. Atmospheric models in radiative and chemical equilibrium that account for the detected species indicate a carbon-rich chemistry with a carbon-to-oxygen ratio close to or greater than 1, higher than the solar value (0.55). According to existing models relating the atmospheric chemistry to planet formation and migration scenarios, this would suggest that HD 209458b formed far from its present location and subsequently migrated inwards.

考古学 Archaeology

Innovative Homo sapiens behaviours 105,000 years ago in a wetter Kalahari

发生在105000年前卡拉哈里盆地中的人类创新行为

作者：Jayne Wilkins, Benjamin J. Schoville, Robyn Pickering, Luke Gliganic, et al.

链接：

摘要

非洲的考古记录为智人复杂的符号和技术行为的出现提供了最早的证据。然而，保存完好、年代学较强的晚更新世地层遗址在南非内陆非常罕见，因此海岸假说仍未得到验证。

在此，我们展示了与大约10.5万年前南部非洲沿海地区的人类发明相似的早期人类发明，他们大约在同一时期生活在600多公里外的内陆地区。我们报告了有意收集非实用物体（方解石晶体）和鸵鸟蛋壳的证据。

这些证据来自对于卡拉哈里盆地南部的一个层状岩石矿床的挖掘现场，我们通过光释光测年技术确定其距今约10.5万年。残存凝灰岩矿床的铀钍定年法表明，这里偶尔会有大量淡水流动；这些岩层中最古老的可以追溯到11至10万年之间，与考古发现相一致。

我们的结果表明，南部非洲内陆人类的创新行为并不落后于靠近海岸的人群，而且这些创新行为可能是在潮湿的大草原环境中发展起来的。

Abstract

The archaeological record of Africa provides the earliest evidence for the emergence of the complex symbolic and technological behaviours that characterize Homo sapiens. However, stratified Late Pleistocene sites with good preservation and robust chronologies are rare in the interior of southern Africa, and the coastal hypothesis therefore remains untested. Here we show that early human innovations that are similar to those dated to around 105 thousand years ago (ka) in coastal southern Africa existed at around the same time among humans who lived over 600 km inland. We report evidence for the intentional collection of non-utilitarian objects (calcite crystals) and ostrich eggshell from excavations of a stratified rockshelter deposit in the southern Kalahari Basin, which we date by optically stimulated luminescence to around 105 ka. Uranium–thorium dating of relict tufa deposits indicates sporadic periods of substantial volumes of fresh, flowing water; the oldest of these episodes is dated to between 110 and 100 ka and is coeval with the archaeological deposit. Our results suggest that behavioural innovations among humans in the interior of southern Africa did not lag behind those of populations near the coast, and that these innovations may have developed within a wet savannah environment.

材料科学 Material Science

Entropic evidence for a Pomeranchuk effect in magic-angle graphene

魔角石墨烯中波梅兰丘克效应的熵证据

作者：Asaf Rozen, Jeong Min Park, Uri Zondiner, Yuan Cao, Daniel Rodan-Legrain, et al.

链接：

摘要

20世纪50年代，波梅兰丘克预测，液态氦-3加热后可能会凝固，这与我们的直觉相反。这种效应是由于固相中原子在空间局部的高过量核自旋熵引起的。在此，我们发现在魔角扭曲双层石墨烯中也发生了类似的效应。

使用局部和全局电子熵测量，我们发现，在每摩尔单胞填充近一个电子时，电子熵显著增加到约每单胞1 k B。这个巨大的过量熵被指向其磁源的平面内磁场淬灭。可压缩性随电子密度的变化而急剧下降，伴随着费米能级的重置回到狄拉克点附近，标志着两相之间的清晰边界。

我们将这种跃变映射为电子密度，温度和磁场的函数。这揭示了一个相图，与波梅兰丘克一样，温度和磁场驱动了从低熵电子液体到具有几乎自由磁矩的高熵相关态转变。

相关态的特征是表面上相互矛盾性质的不寻常组合，一些与流动的电子有关——例如缺乏热力学间隙、金属性和狄拉克式的可压缩性——另一些与局部矩有关，例如大的熵及其在磁场下的消失。

Abstract

In the 1950s, Pomeranchuk predicted that, counterintuitively, liquid 3He may solidify on heating. This effect arises owing to high excess nuclear spin entropy in the solid phase, where the atoms are spatially localized. Here we find that an analogous effect occurs in magic-angle twisted bilayer graphene. Using both local and global electronic entropy measurements, we show that near a filling of one electron per moiré unit cell, there is a marked increase in the electronic entropy to about 1 k B per unit cell ( k B is the Boltzmann constant). This large excess entropy is quenched by an in-plane magnetic field, pointing to its magnetic origin. A sharp drop in the compressibility as a function of the electron density, associated with a reset of the Fermi level back to the vicinity of the Dirac point, marks a clear boundary between two phases. We map this jump as a function of electron density, temperature and magnetic field. This reveals a phase diagram that is consistent with a Pomeranchuk-like temperature- and field-driven transition from a low-entropy electronic liquid to a high-entropy correlated state with nearly free magnetic moments. The correlated state features an unusual combination of seemingly contradictory properties, some associated with itinerant electrons—such as the absence of a thermodynamic gap, metallicity and a Dirac-like compressibility—and others associated with localized moments, such as a large entropy and its disappearance under a magnetic field.

Isospin Pomeranchuk effect in twisted bilayer graphene

扭曲双层石墨烯的同位旋波梅兰丘克效应

作者：Yu Saito, Fangyuan Yang, Jingyuan Ge, Xiaoxue Liu, Takashi Taniguchi, Kenji Watanabe, et al.

链接：

摘要

在此，我们展示了一种机制来描述魔角扭曲双层石墨烯中自旋和波谷同位旋的有限温度动力学。

值得注意的是，在超晶格填充因子 1附近，高温时电阻率出现峰值，而在低温极限时则没有出现相应的相。倾斜磁场的磁输运和面内磁矩的热力学测量表明，电阻率峰值与系统发展为有限同位旋极化的有限场磁相变有关。这些数据提示了一种波梅兰丘克型机制。

在这种机制中，相对于同位旋未极化的费米液相，铁磁相中的无序同位旋矩的熵在更高的温度下使相稳定。

Abstract

Here we show that a similar mechanism describes the finite-temperature dynamics of spin and valley isospins in magic-angle twisted bilayer graphene. Notably, a resistivity peak appears at high temperatures near a superlattice filling factor of 1, despite no signs of a commensurate correlated phase appearing in the low-temperature limit. Tilted-field magnetotransport and thermodynamic measurements of the in-plane magnetic moment show that the resistivity peak is connected to a finite-field magnetic phase transition at which the system develops finite isospin polarization. These data are suggestive of a Pomeranchuk-type mechanism, in which the entropy of disordered isospin moments in the ferromagnetic phase stabilizes the phase relative to an isospin-unpolarized Fermi liquid phase at higher temperatures.

Diversity-oriented synthesis of polymer membranes with ion solvation cages

基于离子溶剂化聚合物膜的多样性取向合成

作者：Miranda J. Baran, Mark E. Carrington, Swagat Sahu, Artem Baskin, Junhua Song, et al.

链接：

摘要

在此，我们描述了一种面向多样性的微孔聚合物膜合成策略，以识别具有FVEs的候选材料，作为锂离子的溶剂笼。

这一策略包括通过曼尼希反应使双联邻苯二酚单体多样化，从而在FVEs中引入锂离子协调功能，加强拓扑聚合使FVEs进入不同的孔结构，以及多种多样的孔几何和介电性能的聚合物反应。

具有离子溶剂化笼的候选膜比控制膜具有更高的离子电导率和更高的阳离子转移数，其中FVEs具有特异性，表明可以克服常规的膜渗透性边界和离子转移的选择性。

Abstract

Here we describe a persity-oriented synthetic strategy for microporous polymer membranes to identify candidates featuring FVEs that serve as solvation cages for lithium ions (Li+). This strategy includes persification of bis(catechol) monomers by Mannich reactions to introduce Li+-coordinating functionality within FVEs, topology-enforcing polymerizations for networking FVEs into different pore architectures, and several on-polymer reactions for persifying pore geometries and dielectric properties. The most promising candidate membranes featuring ion solvation cages exhibited both higher ionic conductivity and higher cation transference number than control membranes, in which FVEs were aspecific, indicating that conventional bounds for membrane permeability and selectivity for ion transport can be overcome.

地球科学 Geoscience

A 200-million-year delay in permanent atmospheric oxygenation

延迟了2亿年的永久大气氧化

作者：Simon W. Poulton, Andrey Bekker, Vivien M. Cumming, Aubrey L. Zerkle, Donald E. Canfield & David T. Johnston

链接：

摘要

早期大气氧化发生在以多次全球冰期为标志的长期极端气候不稳定时期，氧浓度最初上升到目前大气水平的 10- 5 以上的时间则推定为24.3亿年前。然而，随后大气氧含量的波动一直持续到大约23.2亿年前，这代表了大气中不可逆氧化的估计时间。

在此，我们通过南非德兰士瓦尔超群的海洋沉积物，对古代早期最后两次冰期的大气和局部海洋氧化还原条件进行了高分辨率重建。利用多重硫同位素和铁-硫-碳系统，我们证明了大约23.2亿年前之后大气氧水平的持续振荡，这与海洋氧化还原化学和气候的主要扰动有关。

因此，在大约2亿年的时间里，氧气水平在目前大气水平的 10- 5 的阈值上下波动。永久的大氧化事件比目前估计的晚了大约1亿年。

Abstract

Early atmospheric oxygenation occurred over a protracted period of extreme climatic instability marked by multiple global glaciations, with the initial rise of oxygen concentration to above 10- 5 of the present atmospheric level constrained to about 2.43 billion years ago. Subsequent fluctuations in atmospheric oxygen levels have, however, been reported to have occurred until about 2.32 billion years ago, which represents the estimated timing of irreversible oxygenation of the atmosphere. Here we report a high-resolution reconstruction of atmospheric and local oceanic redox conditions across the final two glaciations of the early Palaeoproterozoic era, as documented by marine sediments from the Transvaal Supergroup, South Africa. Using multiple sulfur isotope and iron–sulfur–carbon systematics, we demonstrate continued oscillations in atmospheric oxygen levels after about 2.32 billion years ago that are linked to major perturbations in ocean redox chemistry and climate. Oxygen levels thus fluctuated across the threshold of 10- 5 of the present atmospheric level for about 200 million years, with permanent atmospheric oxygenation finally arriving with the Lomagundi carbon isotope excursion at about 2.22 billion years ago, some 100 million years later than currently estimated.

编译 | 未玖

Nature , 11 February 2021, VOL 590, ISSUE 7845

《自然》 2021年2月11日，第590卷，7845期

物理学 Physics

A quantum enhanced search for dark matter axions 量子增强搜索暗物质轴子 作者：K. M. Backes, D. A. Palken, S. Al Kenany, B. M. Brubaker, S. B. Cahn, A. Droster, et al. 链接： 摘要 在暗物质轴子搜索中，量子不确定性表现为一个基本噪声源，限制了用于探测的正交可观测值的测量。对暗物质的研究很少接近这个极限，到目前为止也无人超越。研究组利用真空压缩来突破量子极限寻找暗物质。通过制备一个压缩状态下的微波频率电磁场，并以近乎无噪声的方式读出压缩正交曲线，研究组可在质量范围内将轴子的搜索速度提高一倍。在16.96-17.12和17.14-17.28微伏的轴子剩余能量窗口中，研究组没有发现暗物质存在的证据。突破量子极限带来了一个基础物理 探索 的时代，与接近量子极限的收益递减相比，降噪技术将带来极大益处。

A universal 3D imaging sensor on a silicon photonics platform 基于硅光子学平台的通用三维成像传感器 作者：Christopher Rogers, Alexander Y. Piggott, David J. Thomson, Robert F. Wiser, Ion E. Opris, Steven A. Fortune, et al. 链接： 摘要 精确的三维（3D）成像对于机器绘制地图和与物理世界交互至关重要。由于难以为每个像素提供电子和光子连接，以前的系统限制在20个像素以下。研究组演示了一个由512个像素组成的大规模相干探测器阵列在3D成像系统中的操作。利用光子和电子电路单片集成的最新进展，将密集的光学外差探测器阵列与集成的电子读出结构相结合，可直接扩展到任意大的阵列。双轴固态光束转向消除了视野和距离之间的任何权衡。在量子噪声极限下，研究组的系统仅使用4毫瓦的光时，在75米的距离可达到3.1毫米的精度，比现有固态系统在该距离内的精度高出一个数量级。未来使用最先进的组件缩小像素尺寸，可为消费者相机传感器大小的阵列提供超过2000万像素的分辨率。该研究成果为低成本、紧凑和高性能的3D成像相机的开发和普及铺平了道路，这些相机可应用于从机器人技术和自主导航到增强现实和医疗保健等领域。

材料科学 Materials Science

Tunable strongly coupled superconductivity in magic-angle twisted trilayer graphene 魔角扭曲三层石墨烯中可调谐的强耦合超导 作者：Jeong Min Park, Yuan Cao, Kenji Watanabe, Takashi Taniguchi & Pablo Jarillo-Herrero 链接： 摘要 魔角扭曲双层石墨烯仍然是唯一一种可重现强超导性的体系。研究组在魔角扭曲三层石墨烯（MATTG）中实现了莫尔超导体，它比魔角扭曲双层石墨烯具有更好的电子结构和超导性能。测量霍尔效应和量子振荡作为密度和电场的函数，研究组能够确定系统在正常金属状态下的可调谐相界。零磁场电阻率测量表明，超导性的存在与每个莫尔晶胞中两个载流子所形成的破缺对称相密切相关。研究组发现超导相被抑制，并被限制在部分环绕着破缺对称相的范霍夫奇点处，这很难与弱耦合Bardeen-Cooper-Schrieffer理论相吻合。此外，该系统广泛的原位可调谐性使其能够达到超强耦合状态，其特征是金兹堡-朗道相干长度达到平均粒子间距离，以及非常大的TBKT/TF值，超过0.1。观察结果表明，MATTG可电调谐至接近二维玻色-爱因斯坦凝聚体的交叉点。研究结果建立了一系列可调谐莫尔超导体，它们有可能彻底改变人们对强耦合超导的基本认识和应用。

Facile route to bulk ultrafine-grain steels for high strength and ductility 一种大规模制备高强度高塑性超细晶钢的简易方法 作者：Junheng Gao, Suihe Jiang, Huairuo Zhang, Yuhe Huang, Dikai Guan, Yidong Xu, et al. 链接： 摘要 亚微米晶粒尺寸的钢通常具有较高的韧性和强度，这使其在轻量化技术和节能战略方面具有广阔的应用前景。迄今为止，超细晶（UFG）合金的工业制备通常依赖于扩散相变的控制，因此仅限于制备奥氏体-铁素体相变的钢。此外，这些UFG钢有限的加工硬化和均匀延伸阻碍了其广泛应用。研究组报道了一种在Fe-22Mn-0.6C孪晶诱导塑性钢中大量制备UFG结构的简易方法，即通过微量铜合金化，以及30秒内相干无序富Cu相的晶内纳米析出控制再结晶过程。快速而大量的纳米析出不仅阻止了新的亚微米级再结晶晶粒的生长，而且还通过齐纳钉扎机制提高了所获得的UFG结构的热稳定性。此外，由于析出相完全的相干性和无序性，在载荷条件下，析出相与位错的相互作用较弱。这种方法能够制备晶粒尺寸为800 400纳米的完全再结晶UFG结构，而不会引入有害的晶格缺陷，如脆性颗粒和晶界偏析。与未添加Cu的钢相比，UFG结构的屈服强度提高了一倍，达到710兆帕左右，均匀延展性为45%，抗拉强度为2000兆帕左右。这种晶粒细化的概念亦可扩展到其他合金系统，并且制造工艺较易应用到现有的工业生产线。

Thermally reconfigurable monoclinic nematic colloidal fluids 热可重构单斜向列相胶体液 作者：Haridas Mundoor, Jin-Sheng Wu, Henricus H. Wensink & Ivan I. Smalyukh 链接： 摘要 迄今为止，除简单结构外，具有很少或没有对称操作的结构已被证明仅是固体的一种性质，而不是它们的完全流体凝聚态对应物的性质，尽管这种对称性在理论上被考虑并在磁胶体中被观察到。研究组证明了在由分子棒组成的向列相主体中分散高各向异性的带电胶体盘，为观察许多低对称相提供了一个平台。根据盘的温度、浓度和表面电荷，研究组发现向列相、近晶相和柱状组织的对称性从单轴转向正交和单斜。随着温度的升高，研究组观察到了从低序状态到高序状态、以及重入相的异常转变。最重要的是，研究组证明了可重构单斜相胶体向列相序的存在，以及低对称性自组装的热控制和磁控制的可能性。研究组的实验结果得到了向列相主体中圆盘间胶体相互作用的理论模型的支持，并有望为在具有不同形状和尺寸的构建块的系统中实现许多低对称凝聚相及其技术应用提供一条途径。

化学 Chemistry

Complex structures arising from the self-assembly of a simple organic salt 简单有机盐自组装形成的复杂结构 作者：Riccardo Montis, Luca Fusaro, Andrea Falqui, Michael B. Hursthouse, Nikolay Tumanov, Simon J. Coles, et al. 链接： 摘要 虽然分子自组装已经被广泛研究，但理解控制这种现象的规则仍具有挑战性。研究组报道了一种简单的氨吡啶盐酸盐结晶为四种不同的结构，其中两种采用了不寻常的自组装组成了氯离子和吡啶离子的多面体团簇。这两种结构代表了刚性有机小分子的Frank–Kasper（FK）相。尽管FK相在60多年前就已在金属合金中发现，但最近已在几类超分子软物质和金纳米晶体超晶格中观察到FK相，并持续至今。在这些体系中，原子或分子的球形组件被组装成配位数为12、14、15或16的多面体。该文报道的两种FK结构是从致密液相结晶出来的，显示出一种在刚性有机小分子中通常无法观察到的复杂性。通过低温电子显微镜对前驱体致密液相的研究，揭示了球形聚集体的存在，其尺寸在1.5到4.6纳米之间。这些结构，连同用于制备它们的实验程序，引起了人们对其形成的有趣猜测，并为有机晶体材料的设计开辟了不同的视角。