自然（20220512出版）一周论文导读

　　编译 | 冯维维
　　Nature , 12 May 2022, Volume 605 Issue 7909
　　《自然》 2022年5月12日，第605卷7909期
　　物理学 Physics
　　Suppression of black-hole growth by strong outflows at redshifts 5.8–6.6
　　红移5.8-6.6时强劲的流出抑制黑洞增长
　　作者：M. Bischetti, C. Feruglio, F. Fiore Show authors
　　链接：
　　https://www.nature.com/articles/s41586-022-04608-1
　　摘要：
　　明亮的类星体，被十亿个太阳质量的黑洞吸积而成，在宇宙5亿~ 10亿年的再电离时期就已经存在了。这些黑洞是如何在如此短的时间内形成的，是一个有争议的话题，尤其是当它们位于黑洞质量与本宇宙中星系动力学质量之间的相关性上时。
　　是什么减缓了黑洞的增长？导致在宇宙中观察到的共生增长？这个过程是何时开始的？这些答案迄今尚不知晓，尽管黑洞反馈可能是一个驱动因素。
　　作者报告在红移5.8 z 6.6的类星体样本的光学和近红外观测。通过追踪由黑洞驱动的风的极端外流速度（高达光速的17%），类星体光谱的约一半显示出宽的蓝移吸收线槽。
　　在z 5.8处存在这种外流风的类星体比例比z 2-4处高约2.4倍。他们推断z 5.8处的流出物向星际介质注入了大量的能量，抑制了核气体的吸积，减缓了黑洞的增长。流出阶段可能标志着大量黑洞反馈的开始。在z 5.8流出的类星体的红色光学颜色确实表明，这些系统满是尘埃，可能会在模糊吸积的初始熄灭阶段被捕捉到。
　　Abstract：
　　Bright quasars, powered by accretion onto billion-solar-mass black holes, already existed at the epoch of reionization, when the Universe was 0.5–1 billion years old1. How these black holes formed in such a short time is the subject of debate, particularly as they lie above the correlation between black-hole mass and galaxy dynamical mass in the local Universe. What slowed down black-hole growth, leading towards the symbiotic growth observed in the local Universe, and when this process started, has hitherto not been known, although black-hole feedback is a likely driver. Here we report optical and near-infrared observations of a sample of quasars at redshifts 5.8   z   6.6. About half of the quasar spectra reveal broad, blueshifted absorption line troughs, tracing black-hole-driven winds with extreme outflow velocities, up to 17% of the speed of light. The fraction of quasars with such outflow winds at z   5.8 is  2.4 times higher than at z   2–4. We infer that outflows at z   5.8 inject large amounts of energy into the interstellar medium and suppress nuclear gas accretion, slowing down black-hole growth. The outflow phase may then mark the beginning of substantial black-hole feedback. The red optical colours of outflow quasars at z   5.8 indeed suggest that these systems are dusty and may be caught during an initial quenching phase of obscured accretion
　　X-ray detection of a nova in the fireball phase
　　用X射线探测到火球阶段的新星
　　作者：Ole König, Jörn Wilms, Riccardo Arcodia, Thomas Dauser, Konrad Dennerl, Victor Doroshenko, Frank Haberl, Steven Hämmerich, Christian Kirsch, Ingo Kreykenbohm, Maximilian Lorenz, Adam Malyali, Andrea Merloni, Arne Rau, Thomas Rauch, Gloria Sala, Axel Schwope, Valery Suleimanov, Philipp Weber & Klaus Werner
　　链接：
　　https://www.nature.com/articles/s41586-022-04635-y
　　摘要：
　　新星的产生是由于富含氢的吸积白矮星的包膜发生失控的热核燃烧，这导致了包膜的快速膨胀和大部分质量的喷射。理论预测，在逃逸的核聚变之后，存在一个＂火球＂阶段，在新星变为可见光之前，应该可以观测到一个短暂、明亮的软X射线闪光。
　　作者报告了在经典银河新星YZ Reticuli的9级磁光学变亮前11小时的一个明亮的软X射线闪光的观测结果。事件发生前4小时和发生后4小时内均未检测到X射线源，这限制了闪光持续时间小于8小时。
　　与理论预测一致的是，该源的光谱形状与一个3.27+0.11 - 0.33   105 K的黑色天体一致，或一个以爱丁顿光度辐射的白矮星大气层一致，其光球只比典型的白矮星略大。
　　Abstract：
　　Novae are caused by runaway thermonuclear burning in the hydrogen-rich envelopes of accreting white dwarfs, which leads to a rapid expansion of the envelope and the ejection of most of its mass. Theory has predicted the existence of a ‘fireball’ phase following directly on from the runaway fusion, which should be observable as a short, bright and soft X-ray flash before the nova becomes visible in the optical. Here we report observations of a bright and soft X-ray flash associated with the classical Galactic nova YZ Reticuli 11 h before its 9 mag optical brightening. No X-ray source was detected 4 h before and after the event, constraining the duration of the flash to shorter than 8 h. In agreement with theoretical predictions, the source’s spectral shape is consistent with a black-body of 3.27+0.11 0.33   105 K (28.2+0.9 2.8 eV), or a white dwarf atmosphere, radiating at the Eddington luminosity, with a photosphere that is only slightly larger than a typical white dwarf.
　　Light-field control of real and virtual charge carriers
　　实和虚载流子的光场控制
　　作者：Tobias Boolakee, Christian Heide, Antonio Garzón-Ramírez, Heiko B. Weber, Ignacio Franco & Peter Hommelhoff
　　链接：
　　https://www.nature.com/articles/s41586-022-04565-9
　　摘要：
　　光驱动电子激发是能量和信息传递的基石。在强超快光场与固体的相互作用中，电子被不可逆地或仅在照明时被瞬态地激发。
　　由于在光脉冲消失后无法观测到瞬态电子布居，因此称为虚电子布居，而仍然处于激发态的电子布居称为实电子布居。虚载流子最近被认为与高谐波产生和瞬态吸收有关，但光电流的产生可能来自真实和虚载流子。然而，载体类型的生成和它们对技术相关性的重要性之间的联系缺失。
　　作者证明了在金-石墨烯-金异质结构中，用低周期激光脉冲可以激发和解缠实和虚载流子产生电流。根据用于光激发的波形，真实载流子接收净动量并传播到金电极，而虚拟载流子产生在金-石墨烯界面读出的极化响应。
　　在此基础上，他们进一步论证了未来光波电子学中逻辑门的概念证明。该结果提供了一种直接的方法来监测和激发实和虚载流子。单独控制每种类型的载波将显著增加集成电路的设计空间，使千赫信号处理更接近现实。
　　Abstract：
　　Light-driven electronic excitation is a cornerstone for energy and information transfer. In the interaction of intense and ultrafast light fields with solids, electrons may be excited irreversibly, or transiently during illumination only. As the transient electron population cannot be observed after the light pulse is gone, it is referred to as virtual, whereas the population that remains excited is called real. Virtual charge carriers have recently been associated with high-harmonic generation and transient absorption, but photocurrent generation may stem from real as well as virtual charge carriers. However, a link between the generation of the carrier types and their importance for observables of technological relevance is missing. Here we show that real and virtual charge carriers can be excited and disentangled in the optical generation of currents in a gold–graphene–gold heterostructure using few-cycle laser pulses. Depending on the waveform used for photoexcitation, real carriers receive net momentum and propagate to the gold electrodes, whereas virtual carriers generate a polarization response read out at the gold–graphene interfaces. On the basis of these insights, we further demonstrate a proof of concept of a logic gate for future lightwave electronics. Our results offer a direct means to monitor and excite real and virtual charge carriers. Inpidual control over each type of carrier will markedly increase the integrated-circuit design space and bring petahertz signal processing closer to reality.
　　化学 Chemistry
　　Stability-limiting heterointerfaces of perovskite photovoltaics
　　钙钛矿光伏的限制稳定性异质界面
　　作者：Shaun Tan, Tianyi Huang, Ilhan Yavuz, Rui Wang, Tae Woong Yoon, Mingjie Xu, Qiyu Xing, Keonwoo Park, Do-Kyoung Lee, Chung-Hao Chen, Ran Zheng, Taegeun Yoon, Yepin Zhao, Hao-Cheng Wang, Dong Meng, Jingjing Xue, Young Jae Song, Xiaoqing Pan, Nam-Gyu Park, Jin-Wook Lee & Yang Yang
　　链接：
　　https://www.nature.com/articles/s41586-022-04604-5
　　摘要：
　　光电子器件由不同半导体材料之间形成的异质界面组成。接触半导体之间的相对能级排列决定了异质界面电荷注入和萃取动力学。
　　对于钙钛矿太阳能电池（PSCs），通常对顶部钙钛矿表面与电荷传输材料之间的异质界面进行缺陷钝化处理，以提高PSCs的稳定性和性能。然而，这种表面处理也会影响异质界面的能量。
　　作者研究表明，表面处理可能会诱导负功函数转移（即更多的n型），这激活了卤化物迁移，从而加剧PSC的不稳定性。
　　因此，尽管表面钝化有有益的影响，但这种有害的副作用限制了以这种方式处理的PSCs的最大稳定性改善。这种有益和有害影响之间的权衡应该指导通过表面处理提高PSC稳定性的进一步工作。
　　Abstract：
　　Optoelectronic devices consist of heterointerfaces formed between dissimilar semiconducting materials. The relative energy-level alignment between contacting semiconductors determinately affects the heterointerface charge injection and extraction dynamics. For perovskite solar cells (PSCs), the heterointerface between the top perovskite surface and a charge-transporting material is often treated for defect passivation1,2,3,4 to improve the PSC stability and performance. However, such surface treatments can also affect the heterointerface energetics1. Here we show that surface treatments may induce a negative work function shift (that is, more n-type), which activates halide migration to aggravate PSC instability. Therefore, despite the beneficial effects of surface passivation, this detrimental side effect limits the maximum stability improvement attainable for PSCs treated in this way. This trade-off between the beneficial and detrimental effects should guide further work on improving PSC stability via surface treatments.
　　Materials synthesis at terapascal static pressures
　　极端压强下的材料合成
　　作者：Leonid Dubrovinsky, Saiana Khandarkhaeva, Timofey Fedotenko, Dominique Laniel, Maxim Bykov, Carlotta Giacobbe, Eleanor Lawrence Bright, Pavel Sedmak, Stella Chariton, Vitali Prakapenka, Alena V. Ponomareva, Ekaterina A. Smirnova, Maxim P. Belov, Ferenc Tasnádi, Nina Shulumba, Florian Trybel, Igor A. Abrikosov & Natalia Dubrovinskaia
　　链接：
　　https://www.nature.com/articles/s41586-022-04550-2
　　摘要：
　　理论模型预测在极端压力和温度条件下，材料具有不寻常的结构和特性。迄今为止，超高压实验的技术复杂性和材料分析的原位方法的缺乏，都阻碍了它们在200 GPa以上的合成和研究。作者报告了一种高压高温合成实验的方法，它将高压结晶学的限制扩展到TPA范围
　　为了达到预期的压力，研究者结合了环形和双级顶砧设计。在激光加热的dsDAC中，在Re-N体系中进行了三次不同的实验，合成了铼氮合金和氮化铼Re7N3 。研究者利用单晶XRD原位对其进行了完整的结构和化学表征。
　　研究者用这种方法，在激光加热的双级金刚石顶砧单元中，实现了压力约为600和900 GPa，获得了铼氮合金，并合成了氮化铼Re7N3 ，正如理论分析表明，只有在极端压缩下才稳定。
　　数兆巴以上的压力，长期以来一直被认为对材料的化学和物理有深远的影响，并导致具有奇异晶体结构相的形成。通过将高压合成和结构研究的实验领域扩展到TPa范围，该研究为新材料的发现和新物理现象的观察铺平了道路。
　　Abstract：
　　Theoretical modelling predicts very unusual structures and properties of materials at extreme pressure and temperature conditions1,2. Hitherto, their synthesis and investigation above 200 gigapascals have been hindered both by the technical complexity of ultrahigh-pressure experiments and by the absence of relevant in situ methods of materials analysis. Here we report on a methodology developed to enable experiments at static compression in the terapascal regime with laser heating. We apply this method to realize pressures of about 600 and 900 gigapascals in a laser-heated double-stage diamond anvil cell3, producing a rhenium–nitrogen alloy and achieving the synthesis of rhenium nitride Re7N3 —which, as our theoretical analysis shows, is only stable under extreme compression. Full chemical and structural characterization of the materials, realized using synchrotron single-crystal X-ray diffraction on microcrystals in situ, demonstrates the capabilities of the methodology to extend high-pressure crystallography to the terapascal regime.
　　生态学 Ecology
　　A global reptile assessment highlights shared conservation needs of tetrapods
　　全球爬行动物的灭绝风险
　　作者：Neil Cox, Bruce E. Young, Yan Xie, etc.
　　链接：
　　https://www.nature.com/articles/s41586-022-04664-7
　　摘要：
　　科学家已经对鸟、哺乳动物、两栖动物开展了全面的灭绝风险评估，但对爬行动物的全面评估一直空白。目前为止，对爬行动物的保育策略一直依赖其他动物在世界自然保护联盟（IUCN）红色名录中的等级以及分布来指导相关政策和行动优先级。
　　作者对全球1万多种爬行动物物种进行了一次全面评估，发现超过21%的物种存在灭绝风险。研究结果显示，需要采取紧急保育行动来防止部分爬行动物走向灭绝，包括许多鳄鱼和乌龟物种。
　　作者使用IUCN红色名录的等级对爬行动物进行了分类，借此评估全球爬行动物的灭绝风险。在10196个评估物种中，他们发现至少有1829（21%）个物种存在灭绝风险（按不同等级分为易危、濒危、极危）。鳄鱼和乌龟属于最容易灭绝的物种，分别有57.9%和50.0%的物种处于濒危状态。
　　他们指出，农业、伐木、城市建设、入侵物种等因素都是对爬行动物构成威胁的来源，但气候变化造成的威胁仍不明确。在森林居住的物种风险更大——也许是因为森林环境中的爬行动物更容易暴露在特定的危险之中。
　　作者指出，爬行动物面临的许多威胁与其他动物种群相似，并认为保护这些动物种群的保育措施——包括栖息地修复和入侵物种控制——或许也对爬行动物有利。但他们提醒道，目前需要采取紧急保育行动来防止一些爬行动物走向绝灭。
　　Abstract：
　　Comprehensive assessments of species’ extinction risks have documented the extinction crisis1 and underpinned strategies for reducing those risks2. Global assessments reveal that, among tetrapods, 40.7% of amphibians, 25.4% of mammals and 13.6% of birds are threatened with extinction3. Because global assessments have been lacking, reptiles have been omitted from conservation-prioritization analyses that encompass other tetrapods4,5,6,7. Reptiles are unusually perse in arid regions, suggesting that they may have different conservation needs6. Here we provide a comprehensive extinction-risk assessment of reptiles and show that at least 1,829 out of 10,196 species (21.1%) are threatened—confirming a previous extrapolation8 and representing 15.6 billion years of phylogenetic persity. Reptiles are threatened by the same major factors that threaten other tetrapods—agriculture, logging, urban development and invasive species—although the threat posed by climate change remains uncertain. Reptiles inhabiting forests, where these threats are strongest, are more threatened than those in arid habitats, contrary to our prediction. Birds, mammals and amphibians are unexpectedly good surrogates for the conservation of reptiles, although threatened reptiles with the smallest ranges tend to be isolated from other threatened tetrapods. Although some reptiles—including most species of crocodiles and turtles—require urgent, targeted action to prevent extinctions, efforts to protect other tetrapods, such as habitat preservation and control of trade and invasive species, will probably also benefit many reptiles.