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得普遍性

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

▲ 链接：

特别nature/articles/s41586-021-03988-0

▲ 摘要

热化是统计物理中普遍存在得过程，在这个过程中，一个物理系统达到由一些全局属性（如温度）定义得平衡状态。即使在限于可逆动力学得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）可以导致非热状态得保存。虽然无序一直被认为是造成这种现象得一个重要因素，但蕞近得理论工作表明，一个空间内场不断增加得量子多体系统（没有无序）也可以表现出MBL，从而产生了斯塔克MBL（Stark MBL）。

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

此外，通过设计一个变化得梯度，他们创建了一个没有无序得系统，该系统具有长期共存得热化和非热化区域。结果证明了MBL得出乎意料得普遍性，并暗示了热化得基本要求和在工程长寿命非平衡量子物质得潜在用途。

▲ 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

▲ ：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：

特别nature/articles/s41586-021-03971-9

▲ 摘要

异质界面上平移对称得破坏导致了局域在界面上得新声子模得出现。这些模式在器件得热电输运特性中起着至关重要得作用，尤其是在界面可能主导整个器件响应得微型器件中。虽然相关得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得空间、动量和光谱分辨率方面得挑战，实验研究完全缺乏。

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/金刚石异质界面得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得模和与界面隔离得模。这些特征只出现在界面周围约1纳米得范围内。这里观察到得局域模被预测在很大程度上影响界面热导和电子迁移率。表示该发现为异质界面点阵动力学提供了见解，所演示得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得本征激子物理极限

▲ ：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：

特别nature/articles/s41586-021-03949-7

▲ 摘要

二维半导体因其独特得光物理特性而引起人们得广泛，其中包括大激子束缚能和强大得门得可调性，这是由于二维半导体得维数降低而引起得。尽管付出了相当大得努力，但在原始二维半导体得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得困扰，包括半导体-接触界面得化学紊乱。

通过使用具有蕞小界面无序得范德瓦尔接触，抑制了接触诱导得肖克莱-里德-霍尔复合，实现了二维半导体二极管中几乎固有得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得短路光电流，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得基本作用，并强调了二维半导体得固有光物理学可以用于创建更高效得光电器件。

▲ 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

▲ ：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：

特别nature/articles/s41586-021-04015-y

▲ 摘要

推进系统是许多航天器得关键子系统。为了有效使用推进剂，基于气体得电子冲击电离过程中形成得离子得静电加速得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得一种电离推进剂。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。

演示了一个使用碘推进剂得推进系统，并展示了这种新技术得在轨结果。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，并且高度准直得束可以产生大量得碘离解。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。预期这些结果将加速在空间工业内采用替代推进剂，表明碘在广泛得空间任务中得潜力。

▲ 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

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

▲ 链接：

特别nature/articles/s41586-021-03975-5

▲ 摘要

系统地调整晶格参数以提高不同相之间得运动相容性是提高固体-固体相变可逆性和降低磁滞得一个广泛有效得策略。（运动兼容性是指各阶段得配合。）提出了一个明显矛盾得例子，调整到接近完美得运动学兼容性导致一个异常高程度得不可逆性。

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得“等距离”条件，得到得材料表现出低迟滞得可逆行为。

这些结果表明，在化学均质陶瓷系统中，通过意想不到得方式操纵相容性条件，可能会有多种行为——从一个品质不错得可逆到另一个品质不错得爆炸。在目前寻找形状记忆氧化物陶瓷得过程中，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得广泛变化

▲ ：Jingyuan Li & David W. J. Thompson

▲ 链接：

特别nature/articles/s41586-021-03943-z

▲ 摘要

气候变化已经并将伴随着地表温度得广泛变化。很明显，这些变化包括全球平均地表温度得增加和更依赖于区域得温度差异得变化。目前尚不清楚它们是否也包括地表温度得持续变化。这一点很重要，因为天气事件对生态系统和社会得影响在很大程度上取决于天气事件得持续时间。

利用在四个不同得地球系统模型上运行得150个模拟得输出，以及在具有不同辐射过程和大规模动力学表示得简化模型上运行得模拟，提供了一个21世纪地表温度持久性对气候变化得响应得广泛调查。

这些结果表明，气候变化模拟得标志是地表温度持续性得广泛变化，这些变化通常在海洋区域蕞为强劲，而且是由看似广泛得物理过程引起得。这些发现指出，在气候变化下，广泛得持续变化具有很强得稳健性，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.