大学自然科学基础第2版考题_自然科学基础知识答案

编译｜冯维维

Nature, 18 November 2021 ,Volume 599 Issue 7885

《自然》2021年11月18日，第599卷7885期

物理学Physics

Observation of Stark many-body localization without disorder

观察斯塔克多体定位的普遍性

▲ 作者：W. Morong, F. Liu, P. Becker, K. S. Collins, L. Feng, A. Kyprianidis, G. Pagano, T. You, A. V. Gorshkov & C. Monroe

▲ 链接：

https://www.nature.com/articles/s41586-021-03988-0

▲ 摘要

　　热化是统计物理中普遍存在的过程，在这个过程中，一个物理系统达到由一些全局属性（如温度）定义的平衡状态。即使在限于可逆动力学的孤立量子多体系统中，热化现象也普遍存在。

　　然而，在这些系统中，还有另一种可能性：多体定位（MBL）可以导致非热状态的保存。虽然无序一直被认为是造成这种现象的一个重要因素，但最近的理论工作表明，一个空间内场不断增加的量子多体系统（没有无序）也可以表现出MBL，从而产生了斯塔克MBL（Stark MBL）。

　　作者在一个捕获离子量子模拟器中实现了斯塔克MBL，并演示了它的关键特性：热化停止和关联的缓慢传播。通过调整离子自旋在有效场梯度中的相互作用，直接观察了它们在各种初始状态下的微观平衡，并应用单位点控制来测量自旋链中不同区域之间的相关性。

　　此外，通过设计一个变化的梯度，他们创建了一个没有无序的系统，该系统具有长期共存的热化和非热化区域。结果证明了MBL的出乎意料的普遍性，并暗示了热化的基本要求和在工程长寿命非平衡量子物质的潜在用途。

▲ Abstract

　　Thermalization is a ubiquitous process of statistical physics, in which a physical system reaches an equilibrium state that is defined by a few global properties such as temperature. Even in isolated quantum many-body systems, limited to reversible dynamics, thermalization typically prevails. However, in these systems, there is another possibility: many-body localization (MBL) can result in preservation of a non-thermal state. While disorder has long been considered an essential ingredient for this phenomenon, recent theoretical work has suggested that a quantum many-body system with a spatially increasing field—but no disorder—can also exhibit MBL4, resulting in ‘Stark MBL’. Here we realize Stark MBL in a trapped-ion quantum simulator and demonstrate its key properties: halting of thermalization and slow propagation of correlations. Tailoring the interactions between ionic spins in an effective field gradient, we directly observe their microscopic equilibration for a variety of initial states, and we apply single-site control to measure correlations between separate regions of the spin chain. Furthermore, by engineering a varying gradient, we create a disorder-free system with coexisting long-lived thermalized and non-thermal regions. The results demonstrate the unexpected generality of MBL, with implications about the fundamental requirements for thermalization and with potential uses in engineering long-lived non-equilibrium quantum matter.

Measuring phonon dispersion at an interface

在界面处测量声子色散

▲ 作者：Ruishi Qi, Ruochen Shi, Yuehui Li, Yuanwei Sun, Mei Wu, Ning Li, Jinlong Du, Kaihui Liu, Chunlin Chen, Ji Chen, Feng Wang, Dapeng Yu, En-Ge Wang & Peng Gao

▲ 链接：

https://www.nature.com/articles/s41586-021-03971-9

▲ 摘要

　　异质界面上平移对称的破坏导致了局域在界面上的新声子模的出现。这些模式在器件的热电输运特性中起着至关重要的作用，尤其是在界面可能主导整个器件响应的微型器件中。虽然相关的理论工作早在几十年前就开始了，但由于在实现探测局域模态所需的空间、动量和光谱分辨率方面的挑战，实验研究完全缺乏。

　　作者利用四维电子能量损失谱技术，直接测量了外延立方氮化硼/金刚石异质界面的局域振动谱和界面声子色散关系。除了大部分声子模外，他们还观察到局域在界面上的模和与界面隔离的模。这些特征只出现在界面周围约1纳米的范围内。这里观察到的局域模被预测在很大程度上影响界面热导和电子迁移率。作者表示该发现为异质界面点阵动力学提供了见解，所演示的实验技术应该在热管理、电子工程和拓扑声子学中有用。

▲ Abstract

　　The breakdown of translational symmetry at heterointerfaces leads to the emergence of new phonon modes localized at the interface. These modes have an essential role in thermal and electrical transport properties in devices, especially in miniature ones wherein the interface may dominate the entire response of the device. Although related theoretical work began decades ago, experimental research is totally absent owing to challenges in achieving the combined spatial, momentum and spectral resolutions required to probe localized modes. Here, using the four-dimensional electron energy-loss spectroscopy technique, we directly measure both the local vibrational spectra and the interface phonon dispersion relation for an epitaxial cubic boron nitride/diamond heterointerface. In addition to bulk phonon modes, we observe modes localized at the interface and modes isolated from the interface. These features appear only within approximately one nanometre around the interface. The localized modes observed here are predicted to substantially affect the interface thermal conductance and electron mobility. Our findings provide insights into lattice dynamics at heterointerfaces, and the demonstrated experimental technique should be useful in thermal management, electrical engineering and topological phononics.

Approaching the intrinsic exciton physics limit in two-dimensional semiconductor diodes

接近二维半导体二极管的本征激子物理极限

▲ 作者：Peng Chen, Timothy L. Atallah, Zhaoyang Lin, Peiqi Wang, Sung-Joon Lee, Junqing Xu, Zhihong Huang, Xidong Duan, Yuan Ping, Yu Huang, Justin R. Caram & Xiangfeng Duan

▲ 链接：

https://www.nature.com/articles/s41586-021-03949-7

▲ 摘要

　　二维半导体因其独特的光物理特性而引起人们的广泛关注，其中包括大激子束缚能和强大的门的可调性，这是由于二维半导体的维数降低而引起的。尽管付出了相当大的努力，但在原始二维半导体的基本光物理和实际设备性能之间仍然存在脱节，这经常受到许多外在因素的困扰，包括半导体-接触界面的化学紊乱。

　　作者通过使用具有最小界面无序的范德瓦尔接触，抑制了接触诱导的肖克莱-里德-霍尔复合，实现了二维半导体二极管中几乎固有的光物理指示器件性能。他们发现激子扩散限制模型很好地解释了电荷密度依赖的短路光电流，这一结果进一步被扫描光电流显微镜所证实。因此，该研究展示了激子扩散和两体激子—电荷俄格复合在二维器件中的基本作用，并强调了二维半导体的固有光物理学可以用于创建更高效的光电器件。

▲ Abstract

　　Two-dimensional (2D) semiconductors have attracted intense interest for their unique photophysical properties, including large exciton binding energies and strong gate tunability, which arise from their reduced dimensionality. Despite considerable efforts, a disconnect persists between the fundamental photophysics in pristine 2D semiconductors and the practical device performances, which are often plagued by many extrinsic factors, including chemical disorder at the semiconductor–contact interface. Here, by using van der Waals contacts with minimal interfacial disorder, we suppress contact-induced Shockley–Read–Hall recombination and realize nearly intrinsic photophysics-dictated device performance in 2D semiconductor diodes. Taken together, we show that an exciton-diffusion-limited model well explains the charge-density-dependent short-circuit photocurrent, a result further confirmed by scanning photocurrent microscopy. We thus demonstrate the fundamental role of exciton diffusion and two-body exciton–charge Auger recombination in 2D devices and highlight that the intrinsic photophysics of 2D semiconductors can be used to create more efficient optoelectronic devices.

In-orbit demonstration of an iodine electric propulsion system

碘电推进系统在轨演示

▲ 作者：Dmytro Rafalskyi, Javier Martínez Martínez, Lui Habl, Elena Zorzoli Rossi, Plamen Proynov, Antoine Boré, Thomas Baret, Antoine Poyet, Trevor Lafleur, Stanislav Dudin & Ane Aanesland

▲ 链接：

https://www.nature.com/articles/s41586-021-04015-y

▲ 摘要

　　推进系统是许多航天器的关键子系统。为了有效使用推进剂，基于气体的电子冲击电离过程中形成的离子的静电加速的电力推进系统特别有吸引力。

　　目前，氙几乎只被用作空间推进的一种电离推进剂。然而，氙很稀有，它必须在高压下储存，而且商业化生产成本很高。

　　作者演示了一个使用碘推进剂的推进系统，并展示了这种新技术的在轨结果。双原子碘以固体形式储存并在低温下升华。然后用射频感应天线产生等离子体，研究表明电离效率比氙气提高。

　　原子和分子碘离子都被高压栅极加速以产生推力，并且高度准直的束可以产生大量的碘离解。推进系统已经成功地在空间中一颗小卫星上操作，使用卫星跟踪数据确认操作。作者预期这些结果将加速在空间工业内采用替代推进剂，表明碘在广泛的空间任务中的潜力。

▲ Abstract

　　Propulsion is a critical subsystem of many spacecraft. For efficient propellant usage, electric propulsion systems based on the electrostatic acceleration of ions formed during electron impact ionization of a gas are particularly attractive. At present, xenon is used almost exclusively as an ionizable propellant for space propulsion. However, xenon is rare, it must be stored under high pressure and commercial production is expensive. Here we demonstrate a propulsion system that uses iodine propellant and we present in-orbit results of this new technology. Diatomic iodine is stored as a solid and sublimated at low temperatures. A plasma is then produced with a radio-frequency inductive antenna, and we show that the ionization efficiency is enhanced compared with xenon. Both atomic and molecular iodine ions are accelerated by high-voltage grids to generate thrust, and a highly collimated beam can be produced with substantial iodine dissociation. The propulsion system has been successfully operated in space onboard a small satellite with manoeuvres confirmed using satellite tracking data. We anticipate that these results will accelerate the adoption of alternative propellants within the space industry and demonstrate the potential of iodine for a wide range of space missions.

化学Chemistry

Exploding and weeping ceramics

爆炸和渗水陶瓷

▲ 作者：Hanlin Gu, Jascha Rohmer, Justin Jetter, Andriy Lotnyk, Lorenz Kienle, Eckhard Quandt & Richard D. James

▲ 链接：

https://www.nature.com/articles/s41586-021-03975-5

▲ 摘要

　　系统地调整晶格参数以提高不同相之间的运动相容性是提高固体-固体相变可逆性和降低磁滞的一个广泛有效的策略。（运动兼容性是指各阶段的配合。）作者提出了一个明显矛盾的例子，调整到接近完美的运动学兼容性导致一个异常高程度的不可逆性。

　　具体来说，当对运动兼容陶瓷（Zr/Hf）O2(YNb)O4进行四方到单斜相转变冷却时，多晶会缓慢而稳定地在其晶界处解体，甚至爆炸解体。如果调整晶格参数以满足更强的“等距离”条件，得到的材料表现出低迟滞的可逆行为。

　　这些结果表明，在化学均质陶瓷系统中，通过意想不到的方式操纵相容性条件，可能会有多种行为——从一个极端的可逆到另一个极端的爆炸。在目前寻找形状记忆氧化物陶瓷的过程中，这些概念可能至关重要。

▲ Abstract

　　The systematic tuning of crystal lattice parameters to achieve improved kinematic compatibility between different phases is a broadly effective strategy for improving the reversibility, and lowering the hysteresis, of solid–solid phase transformations. (Kinematic compatibility refers to the fitting together of the phases.) Here we present an apparently paradoxical example in which tuning to near perfect kinematic compatibility results in an unusually high degree of irreversibility. Specifically, when cooling the kinematically compatible ceramic (Zr/Hf)O2(YNb)O4 through its tetragonal-to-monoclinic phase transformation, the polycrystal slowly and steadily falls apart at its grain boundaries (a process we term weeping) or even explosively disintegrates. If instead we tune the lattice parameters to satisfy a stronger ‘equidistance’ condition (which additionally takes into account sample shape), the resulting material exhibits reversible behaviour with low hysteresis. These results show that a diversity of behaviours—from reversible at one extreme to explosive at the other—is possible in a chemically homogeneous ceramic system by manipulating conditions of compatibility in unexpected ways. These concepts could prove critical in the current search for a shape-memory oxide ceramic.

气候学Climatology

Widespread changes in surface temperature persistence under climate change

气候变化下地表温度持续性的广泛变化

▲ 作者：Jingyuan Li & David W. J. Thompson

▲ 链接：

https://www.nature.com/articles/s41586-021-03943-z

▲ 摘要

　　气候变化已经并将伴随着地表温度的广泛变化。很明显，这些变化包括全球平均地表温度的增加和更依赖于区域的温度差异的变化。目前尚不清楚它们是否也包括地表温度的持续变化。这一点很重要，因为天气事件对生态系统和社会的影响在很大程度上取决于天气事件的持续时间。

　　作者利用在四个不同的地球系统模型上运行的150个模拟的输出，以及在具有不同辐射过程和大规模动力学表示的简化模型上运行的模拟，提供了一个21世纪地表温度持久性对气候变化的响应的广泛调查。

　　这些结果表明，气候变化模拟的标志是地表温度持续性的广泛变化，这些变化通常在海洋区域最为强劲，而且是由看似广泛的物理过程引起的。这些发现指出，在气候变化下，广泛的持续变化具有很强的稳健性，而且有必要更好地理解、模拟和限制这种变化。

▲ Abstract

　　Climate change has been and will be accompanied by widespread changes in surface temperature. It is clear that these changes include global-wide increases in mean surface temperature and changes in temperature variance that are more regionally-dependent. It is less clear whether they also include changes in the persistence of surface temperature. This is important as the effects of weather events on ecosystems and society depend critically on the length of the event. Here we provide an extensive survey of the response of surface temperature persistence to climate change over the twenty-first century from the output of 150 simulations run on four different Earth system models, and from simulations run on simplified models with varying representations of radiative processes and large-scale dynamics. Together, the results indicate that climate change simulations are marked by widespread changes in surface temperature persistence that are generally most robust over ocean areas and arise due to a seemingly broad range of physical processes. The findings point to both the robustness of widespread changes in persistence under climate change, and the critical need to better understand, simulate and constrain such changes.