团簇光谱与动力学研究进展论文

编译 | 未玖

Science , 06 AUGUST 2021, VOL 373, ISSUE 6555

《科学》 2021年8月6日，第373卷，6555期

物理学 Physics

Quantum-enhanced sensing of displacements and electric fields with two-dimensional trapped-ion crystals

二维捕获离子晶体对位移和电场的量子增强传感

作者：Kevin A. Gilmore, Matthew Affolter, Robert J. Lewis-Swan, Diego Barberena, Elena Jordan, Ana Maria Rey.

链接：

摘要

完全可控的超冷原子系统正在为量子传感创造机会，但通过利用纠缠展示有价值应用中的量子优势仍然是一项具有挑战性的任务。

研究组实现了一个多体量子增强传感器，使用约150个捕获离子的晶体来探测位移和电场。晶体的质心振动模式作为高Q机械振荡器，集体电子自旋作为测量装置。

通过纠缠振荡器和集体自旋，并通过多体回波控制相干动力学，位移被映射为自旋旋转，同时避免了量子反作用和热噪声。

研究组实现了低于标准量子极限8.8 0.4分贝的位移灵敏度，以及在1秒内测量240 10纳伏/米的电场灵敏度。适当改进后应该能够利用捕获离子来寻找暗物质。

Abstract

Fully controllable ultracold atomic systems are creating opportunities for quantum sensing, yet demonstrating a quantum advantage in useful applications by harnessing entanglement remains a challenging task. Here, we realize a many-body quantum-enhanced sensor to detect displacements and electric fields using a crystal of ~150 trapped ions. The center-of-mass vibrational mode of the crystal serves as a high-Q mechanical oscillator, and the collective electronic spin serves as the measurement device. By entangling the oscillator and collective spin and controlling the coherent dynamics via a many-body echo, a displacement is mapped into a spin rotation while avoiding quantum back-action and thermal noise. We achieve a sensitivity to displacements of 8.8 0.4 decibels below the standard quantum limit and a sensitivity for measuring electric fields of 240 10 nanovolts per meter in 1 second. Feasible improvements should enable the use of trapped ions in searches for dark matter.

Modeling of emergent memory and voltage spiking in ionic transport through angstrom-scale slits

埃级别狭缝离子输运中的新兴记忆和电压尖峰模型

作者：Paul Robin, Nikita Kavokine, Lydéric Bocquet.

链接：

摘要

纳米流体学的最新进展使水能够限制在单个分子层内。这种单分子层电解质有望通过离子传输的分子控制实现生物激发功能。然而，人们对这些体系中的离子动力学的了解仍然很少。

研究组发展了一个由分子动力学模拟支持的分析理论，该理论预测了离子输运在准二维狭缝中的强非线性效应。

研究组发现，在电场作用下，离子聚集成细长的团簇，其缓慢的动力学行为导致滞后传导。这种现象被称为忆阻效应，可以用来构建基本神经元。

作为概念证明，研究组对两个纳米流体狭缝进行了分子模拟，重现了霍奇金-赫胥黎模型，并观察了具有神经形态活动特征的电压尖峰自发发射。

Abstract

Recent advances in nanofluidics have enabled the confinement of water down to a single molecular layer. Such monolayer electrolytes show promise in achieving bioinspired functionalities through molecular control of ion transport. However, the understanding of ion dynamics in these systems is still scarce. Here, we develop an analytical theory, backed up by molecular dynamics simulations, that predicts strongly nonlinear effects in ion transport across quasi–two-dimensional slits. We show that under an electric field, ions assemble into elongated clusters, whose slow dynamics result in hysteretic conduction. This phenomenon, known as the memristor effect, can be harnessed to build an elementary neuron. As a proof of concept, we carry out molecular simulations of two nanofluidic slits that reproduce the Hodgkin-Huxley model and observe spontaneous emission of voltage spikes characteristic of neuromorphic activity.

材料科学 Materials Science

Suppressing atomic diffusion with the Schwarz crystal structure in supersaturated Al–Mg alloys

施瓦茨晶体结构抑制过饱和铝镁合金中的原子扩散

作者：W. Xu, B. Zhang, X. Y. Li, K. Lu.

链接：

摘要

金属中的高原子扩散率可通过调整扩散过程实现其结构和性能的可调性，但这会导致其定制性能在高温下不稳定。通过制造单晶或大量合金化消除扩散界面有助于解决这一问题，但不会抑制高同系温度下的原子扩散。

研究组发现施瓦茨晶体结构在具有极细晶粒的过饱和铝镁合金中可有效抑制原子扩散。通过形成这些稳定的结构，纳米晶粒中扩散控制的金属间化合物析出及其粗化被抑制到平衡熔化温度，在此温度附近，表观跨边界扩散率降低了约七个数量级。

利用施瓦茨晶体结构开发先进的高温应用工程合金意义重大。

Abstract

High atomic diffusivity in metals enables substantial tuneability of their structure and properties by tailoring the diffusional processes, but this causes their customized properties to be unstable at elevated temperatures. Eliminating diffusive interfaces by fabricating single crystals or heavily alloying helps to address this issue but does not inhibit atomic diffusion at high homologous temperatures. We discovered that the Schwarz crystal structure was effective at suppressing atomic diffusion in a supersaturated aluminum–magnesium alloy with extremely fine grains. By forming these stable structures, diffusion-controlled intermetallic precipitation from the nanosized grains and their coarsening were inhibited up to the equilibrium melting temperature, around which the apparent across-boundary diffusivity was reduced by about seven orders of magnitude. Developing advanced engineering alloys using the Schwarz crystal structure may lead to useful properties for high-temperature applications.

Hierarchical-morphology metafabric for scalable passive daytime radiative cooling

被动日间辐射冷却的形态分级超材料织物

作者：Shaoning Zeng, Sijie Pian, Minyu Su, Zhuning Wang, Maoqi Wu, Xinhang Liu, et al.

链接：

摘要

将被动辐射冷却结构融入个人热管理技术可有效保护人类免受日益加剧的全球气候变化影响。

研究组发现，由于整个超材料织物中随机分散的散射体的形态分级设计，大规模编织的超材料织物可在大气窗口中具有94.5%的高发射率，在太阳光谱中具有92.4%的高反射率。

通过可扩展的工业纺织品制造路线，研究组的超材料织物在保持高辐射冷却能力的同时，展现出了商业服装理想的机械强度、防水性和透气性。实际应用测试表明，这种超材料织物覆盖的人体温度可比商用棉织物覆盖的人体温度低约4.8 。

超材料织物的成本效益和高性能为智能服装、智能纺织品和被动辐射冷却应用提供了巨大优势。

Abstract

Incorporating passive radiative cooling structures into personal thermal management technologies could effectively defend humans against intensifying global climate change. We show that large-scale woven metafabrics can provide high emissivity (94.5%) in the atmospheric window and high reflectivity (92.4%) in the solar spectrum because of the hierarchical-morphology design of the randomly dispersed scatterers throughout the metafabric. Through scalable industrial textile manufacturing routes, our metafabrics exhibit desirable mechanical strength, waterproofness, and breathability for commercial clothing while maintaining efficient radiative cooling ability. Practical application tests demonstrated that a human body covered by our metafabric could be cooled ~4.8 C lower than one covered by commercial cotton fabric. The cost-effectiveness and high performance of our metafabrics present substantial advantages for intelligent garments, smart textiles, and passive radiative cooling applications.

Semiconductor quantum dots: Technological progress and future challenges

半导体量子点：技术进步与未来挑战

作者：F. Pelayo García de Arquer, Dmitri V. Talapin, Victor I. Klimov, Yasuhiko Arakawa, Manfred Bayer, Edward H. Sargent.

链接：

摘要

在量子限域的半导体纳米结构中，电子表现出与块状固体不同的行为。这使得设计具有可调化学、物理、电学和光学特性的材料成为可能。

零维半导体量子点（QD）在可见光和红外波长范围内具有较强的光吸收和明亮的窄带发射，并已被设计用于显示器件光学增益和激光。这些特性对成像、太阳能采集、显示和通信都很有意义。

研究组详述了量子点纳米材料的合成和机理进展，重点介绍了胶体量子点，并讨论了它们在显示与照明、激光、传感、电子、太阳能转换、光催化和量子信息等技术方面的前景。

Abstract

In quantum-confined semiconductor nanostructures, electrons exhibit distinctive behavior compared with that in bulk solids. This enables the design of materials with tunable chemical, physical, electrical, and optical properties. Zero-dimensional semiconductor quantum dots (QDs) offer strong light absorption and bright narrowband emission across the visible and infrared wavelengths and have been engineered to exhibit optical gain and lasing. These properties are of interest for imaging, solar energy harvesting, displays, and communications. Here, we offer an overview of advances in the synthesis and understanding of QD nanomaterials, with a focus on colloidal QDs, and discuss their prospects in technologies such as displays and lighting, lasers, sensing, electronics, solar energy conversion, photocatalysis, and quantum information.

化学 Chemistry

Watching a hydroperoxyalkyl radical (•QOOH) dissociate

观察氢过氧烷基自由基（•QOOH）离解

作者：Anne S. Hansen, Trisha Bhagde, Kevin B. Moore III, Daniel R. Moberg, Ahren W. Jasper, Yuri Georgievskii, et al.

链接：

摘要

通过红外指纹图谱，研究人员可直接观察到一种在挥发性有机化合物氧化过程中短暂形成的典型氢过氧烷基自由基（•QOOH）中间体，可能量依赖性单分子衰变为羟基自由基和环醚产物。

在宽能量范围内，•QOOH单分子离解率直接时域测量的结果，与使用最先进的过渡态势垒区电子结构表征的理论预测结果一致。

大量重原子隧穿增强了单分子衰变，包括沿反应途径的O-O延伸和C-C-O角收缩。主方程模型对•QOOH中间体的压力依赖性热单分子离解率进行了全面的先验预测（重原子隧穿再次增加了该离解率），这是大气化学和燃烧化学全球模型所需的。

Abstract

A prototypical hydroperoxyalkyl radical (•QOOH) intermediate, transiently formed in the oxidation of volatile organic compounds, was directly observed through its infrared fingerprint and energy-dependent unimolecular decay to hydroxyl radical and cyclic ether products. Direct time-domain measurements of •QOOH unimolecular dissociation rates over a wide range of energies were found to be in accord with those predicted theoretically using state-of-the-art electronic structure characterizations of the transition state barrier region. Unimolecular decay was enhanced by substantial heavy-atom tunneling involving O-O elongation and C-C-O angle contraction along the reaction pathway. Master equation modeling yielded a fully a priori prediction of the pressure-dependent thermal unimolecular dissociation rates for the •QOOH intermediate—again increased by heavy-atom tunneling—which are required for global models of atmospheric and combustion chemistry.