鲁达 编译 | 李言
Nature, 4 November 2021, Volume 599 Issue 7883
《自然》2021年11月4日，第599卷，7883期
材料科学Material Science
Reconstruction of Bloch wavefunctions of holes in a semiconductor
半导体空穴中布洛赫波函数的重建
▲ 作者：J. B. Costello, S. D. O’Hara, Q. Wu, D. C. Valovcin, L. N. Pfeiffer, K. W. West & M. S. Sherwin
▲ 链接：
▲ 摘要
在高阶边带产生中，近红外激光在半导体中产生的电子和空穴被强太赫兹场加速到高动能，并在散射前反冲发射近红外边带。
在此，我们通过实验测量边带极化，并引入一个理论，将这些极化与不同的回忆路径之间的量子干涉联系起来，重建了砷化镓中两种类型的空穴在波长远长于原子间距的波长下的布洛赫波函数。这些布洛赫波函数在球体的表面上紧密可见。 原则上，任何直接间隙半导体或绝缘体都可以观察到高阶边带产生。
因此，我们期望这里介绍的方法可以用于重建这些材料中的低能量布洛赫波函数，从而对凝聚态物质的电子和光学性质的起源和工程有重要的见解。
▲ Abstract
In high-order sideband generation, electrons and holes generated in semiconductors by a near-infrared laser are accelerated to a high kinetic energy by a strong terahertz field, and recollide to emit near-infrared sidebands before they are scattered. Here we reconstruct the Bloch wavefunctions of two types of hole in gallium arsenide at wavelengths much longer than the spacing between atoms by experimentally measuring sideband polarizations and introducing an elegant theory that ties those polarizations to quantum interference between different recollision pathways. These Bloch wavefunctions are compactly visualized on the surface of a sphere. High-order sideband generation can, in principle, be observed from any direct-gap semiconductor or insulator. We thus expect that the method introduced here can be used to reconstruct low-energy Bloch wavefunctions in many of these materials, enabling important insights into the origin and engineering of the electronic and optical properties of condensed matter.
Percolation transitions in compressed SiO2 glasses
压缩二氧化硅玻璃中的渗透转变
▲ 作者：A. Hasmy, S. Ispas & B. Hehlen
▲ 链接：
▲ 摘要
在此，我们报告了压缩二氧化硅玻璃的从头计算，表明结构变化从低到高密度的非晶结构发生了一系列的渗透跃迁。
当压力增加到82 GPa时，在临界压力下，一系列由角或边共享的四面体、五面体和最终八面体组成的长程（“无限”）渗流团簇出现，取代了之前的低折叠协调多面体和低连通性的“阶段”。这一机制为众所周知的3 GPa左右的机械异常以及超过10 GPa的结构不可逆性等特征提供了一个自然的解释。
一些已经发现的非晶结构与最近报道的科石晶IV和V晶体相似，突出了SiO5五面体基多晶在玻璃状二氧化硅致密化过程中的主要作用。我们的研究结果表明，渗流理论为理解非晶-非晶相变的性质和途径提供了一个坚实的框架，并为预测解开的非晶固态和相关液相开辟了新的途径。
▲ Abstract
Here we report ab initio-based calculations of compressed silica (SiO2) glasses, showing that the structural changes from low- to high-density amorphous structures occur through a sequence of percolation transitions. When the pressure is increased to 82 GPa, a series of long-range (‘infinite’) percolating clusters composed of corner- or edge-shared tetrahedra, pentahedra and eventually octahedra emerge at critical pressures and replace the previous ‘phase’ of lower-fold coordinated polyhedra and lower connectivity. This mechanism provides a natural explanation for the well-known mechanical anomaly around 3 GPa, as well as the structural irreversibility beyond 10 GPa, among other features. Some of the amorphous structures that have been discovered mimic those of coesite IV and V crystals reported recently, highlighting the major role of SiO5 pentahedron-based polyamorphs in the densification process of vitreous silica. Our results demonstrate that percolation theory provides a robust framework to understand the nature and pathway of amorphous–amorphous transformations and open a new avenue to predict unravelled amorphous solid states and related liquid phases.
Transition metal-catalysed molecular n-doping of organic semiconductors
过渡金属催化有机半导体分子n-型掺杂
▲ 作者：Han Guo, Chi-Yuan Yang, Xianhe Zhang, Alessandro Motta, Kui Feng, Yu Xia, Yongqiang Shi, Ziang Wu, Kun Yang, Jianhua Chen, Qiaogan Liao, Yumin Tang, Huiliang Sun, Han Young Woo, Simone Fabiano, Antonio Facchetti & Xugang Guo
▲ 链接：
▲ 摘要
在此，我们展示了使用空气稳定前驱体型分子掺杂的有机半导体催化n-型掺杂的一般概念。
通过实验和理论证据评估，过渡金属（例如，Pt, Au, Pd）作为气相沉积的纳米颗粒或溶液可处理的有机金属配合物（例如，Pd2(dba)3）的掺入催化反应， 在较短的掺杂时间内，η值显著提高，电导率高（大于100 S cm−1; ref）。
该方法对实现改进的半导体器件具有技术意义，并为催化剂、分子掺杂剂和半导体三元体系提供了广阔的探索空间，从而为n-型掺杂的研究和应用开辟了新的机遇。
▲ Abstract
Here we show a general concept of catalysed n-doping of organic semiconductors using air-stable precursor-type molecular dopants. Incorporation of a transition metal (for example, Pt, Au, Pd) as vapour-deposited nanoparticles or solution-processable organometallic complexes (for example, Pd2(dba)3) catalyses the reaction, as assessed by experimental and theoretical evidence, enabling greatly increased η in a much shorter doping time and high electrical conductivities (above 100 S cm−1; ref.). This methodology has technological implications for realizing improved semiconductor devices and offers a broad exploration space of ternary systems comprising catalysts, molecular dopants and semiconductors, thus opening new opportunities in n-doping research and applications.
信息技术Information Technology
Experimental relativistic zero-knowledge proofs
实验相对论零知识证明
▲ 作者：Pouriya Alikhani, Nicolas Brunner, Claude Crépeau, Sébastien Designolle, Raphaël Houlmann, Weixu Shi, Nan Yang & Hugo Zbinden
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▲ 摘要
在当今信息化时代，保密是一项重大挑战。计算机科学的发展通过零知识证明的概念提供了一个优雅的解决方案：证明者可以说服验证者某一陈述的有效性，而根本不需要对证明进行详细阐述。
在这项研究中，我们报告了这种零知识协议的实验实现，涉及两个分离的验证者-验证者对。安全性是通过狭义相对论的物理原理来实施的，不需要计算假设（例如单向函数的存在）。
我们的实施完全依赖于现成的设备，无论长（≥400米）或短（60米）距离都在1秒内起效。这证明了多验证者零知识协议的实际潜力，在身份识别任务和区块链应用（如加密货币或智能合约）方面很有前景。
▲ Abstract
Protecting secrets is a key challenge in our contemporary information-based era. Developments in computer science provide an elegant solution via the concept of zero-knowledge proofs: a prover can convince a verifier of the validity of a certain statement without facilitating the elaboration of a proof at all. In this work, we report the experimental realization of such a zero-knowledge protocol involving two separated verifier–prover pairs. Security is enforced via the physical principle of special relativity, and no computational assumption (such as the existence of one-way functions) is required. Our implementation exclusively relies on off-the-shelf equipment and works at both short (60 m) and long distances (≥400 m) in about one second. This demonstrates the practical potential of multi-prover zero-knowledge protocols, promising for identification tasks and blockchain applications such as cryptocurrencies or smart contracts.
地球科学Geoscience
Episodic deluges in simulated hothouse climates
模拟温室气候中的偶发洪水
▲ 作者：Jacob T. Seeley & Robin D. Wordsworth
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▲ 摘要
以前的工作表明，这可能导致温度逆温和云层覆盖的重大变化，但之前的温室制度模型没有直接解决对流尺度的湍流空气运动和云层覆盖，因此留下了许多温室辐射加热的问题没有答案。
在此，我们的模拟明确解决了对流问题，并发现温室气候中的低对流层辐射加热导致水文循环从准稳定状态转变为“松弛振荡”状态——在这种状态下，发生在短而强烈的降水，间隔着多天的干旱期。
向振荡状态的转变伴随着当地降水通量的强烈增强，云层覆盖的大量增加，以及一个短暂的正向（不稳定）气候反馈参数。我们的研究结果表明，温室气候可能具有一种“暂时”对流自组织的新形式，并对云层覆盖和侵蚀过程都有影响。
▲ Abstract
Previous work has suggested that this could lead to temperature inversions and substantial changes in cloud cover, but no previous modelling of the hothouse regime has resolved convective-scale turbulent air motions and cloud cover directly, thus leaving many questions about hothouse radiative heating unanswered. Here we conduct simulations that explicitly resolve convection and find that lower-tropospheric radiative heating in hothouse climates causes the hydrologic cycle to shift from a quasi-steady regime to a ‘relaxation oscillator’ regime, in which precipitation occurs in short and intense outbursts separated by multi-day dry spells. The transition to the oscillatory regime is accompanied by strongly enhanced local precipitation fluxes, a substantial increase in cloud cover, and a transiently positive (unstable) climate feedback parameter. Our results indicate that hothouse climates may feature a novel form of ‘temporal’ convective self-organization, with implications for both cloud coverage and erosion processes.
经济学Economics
Carbon implications of marginal oils from market-derived demand shocks
来自市场需求冲击的边际石油对碳的影响
▲ 作者：Mohammad S. Masnadi, Giacomo Benini, Hassan M. El-Houjeiri, Alice Milivinti, James E. Anderson, Timothy J. Wallington, Robert De Kleine, Valerio Dotti, Patrick Jochem & Adam R. Brandt
▲ 链接：
▲ 摘要
我们探讨了边际原油来源的生命周期温室气体排放影响，确定了对石油需求下降（例如，由于转向替代汽车）最敏感的生产者的上游碳强度（CI）。
我们将1933个油田（约占2015年全球供应量的90%）的生产盈利能力计量模型与它们的生产CI联系起来。然后，我们在3种石油市场结构下考察它们对需求下降的反应。
据我们估算，小的需求冲击与大的冲击具有不同的上游CI影响。不管市场结构如何，小冲击（需求−2.5%）取代的主要是重质原油，其CI比全球平均水平高出25-54%。
然而，当冲击变得更大时，如果具有市场力量的生产者协调应对需求下降，这种不平衡就会减弱。减少石油需求的碳排放效益系统地取决于需求下降的幅度和全球石油市场结构。
▲ Abstract
We explore the life-cycle greenhouse gas emissions impacts of marginal crude sources, identifying the upstream carbon intensity (CI) of the producers most sensitive to an oil demand decline (for example, due to a shift to alternative vehicles). We link econometric models of production profitability of 1,933 oilfields (~90% of the 2015 world supply) with their production CI. Then, we examine their response to a decline in demand under three oil market structures. According to our estimates, small demand shocks have different upstream CI implications than large shocks. Irrespective of the market structure, small shocks (−2.5% demand) displace mostly heavy crudes with ~25–54% higher CI than that of the global average. However, this imbalance diminishes as the shocks become bigger and if producers with market power coordinate their response to a demand decline. The carbon emissions benefits of reduction in oil demand are systematically dependent on the magnitude of demand drop and the global oil market structure.