海洋地球物理学 -海洋地球物理学就业前景

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翻译 | 宗华

Science, 29 November2019, VOL 366, ISSUE6469

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《科学》2019年11月29日，第366卷，6469期

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电磁学Electromagnetism

Mutual control of coherent spin waves and magnetic domain walls in a magnonic device

磁振子器件中磁畴壁与自旋波的相互控制

作者：Jiahao Han, Pengxiang Zhang, Justin T. Hou,et al

链接：

https://science.sciencemag.org/content/366/6469/1121

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摘要：

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自旋波器件的成功实现需要对自旋波的传播进行有效的调制。利用钴镍多层膜，我们通过实验证明纳米尺度的磁畴壁可以以非挥发性的方式控制相干自旋波的相位和幅度。

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我们进一步证明，自旋波可通过磁子自旋电流产生的自旋传递力矩效应被用于改变磁畴壁的位置。

自旋波和磁畴壁之间的相互作用为实现全磁子自旋电子器件提供了可能，其中自旋波信号可通过重新配置磁畴结构被用于控制其他自旋波信号。

Abstract

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The successful implementation of spin-wave devices requires efficient modulation of spin-wave propagation. Using cobalt/nickel multilayer films, we experimentally demonstrate that nanometer-wide magnetic domain walls can be applied to manipulate the phase and magnitude of coherent spin waves in a nonvolatile manner. We further show that a spin wave can, in turn, be used to change the position of magnetic domain walls by means of the spin-transfer torque effect generated from magnon spin current. This mutual interaction between spin waves and magnetic domain walls opens up the possibility of realizing all-magnon spintronic devices, in which one spin-wave signal can be used to control others by reconfiguring magnetic domain structures.

Magnetization switching by magnon-mediated spin torque through an antiferromagnetic insulator

通过反铁磁绝缘体的磁子介导自旋转矩实现磁化开关

作者：Yi Wang, Dapeng Zhu, Yumeng Yang, et al

链接：

https://science.sciencemag.org/content/366/6469/1125

摘要：

磁性器件的广泛应用需要一种有效的方法来控制局部磁化。一种机制是与电子介导的自旋电流相关的电自旋传递转矩。然而，这会遇到焦耳加热造成的大量能量耗散。

我们通过实验展示了一种基于磁子电流的替代方法，并在室温下实现了Bi2Se3/反铁磁绝缘体NiO/铁磁器件中的磁子力矩诱导磁化开关。

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磁子电流可有效携带自旋角动量，而不需要移动电子穿过25纳米厚的NiO层。磁子的转矩足以控制磁化，这与之前观察到的电自旋转矩的比例相当。

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这项研究与自旋电子器件的节能控制有关，将为磁基存储器和逻辑器件的开发注入活力。

Abstract

Widespread applications of magnetic devices require an efficient means to manipulate the local magnetization. One mechanism is the electrical spin-transfer torque associated with electron-mediated spin currents; however, this suffers from substantial energy dissipation caused by Joule heating. We experimentally demonstrated an alternative approach based on magnon currents and achieved magnon-torque–induced magnetization switching in Bi2Se3/antiferromagnetic insulator NiO/ferromagnet devices at room temperature. The magnon currents carry spin angular momentum efficiently without involving moving electrons through a 25-nanometer-thick NiO layer. The magnon torque is sufficient to control the magnetization, which is comparable with previously observed electrical spin torque ratios. This research, which is relevant to the energy-efficient control of spintronic devices, will invigorate magnon-based memory and logic devices.

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材料科学Materials Science

Quantum units from the topological engineering of molecular graphenoids

来自分子石墨烯拓扑改造的量子单元

作者：Federico Lombardi, Alessandro Lodi, Ji Ma, et al

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链接：

https://science.sciencemag.org/content/366/6469/1107

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摘要：

能被集成到设备中的鲁棒相干自旋中心是量子技术的关键组成部分。半导体中的空位是很好的选择，同时理论预测共轭碳材料中的缺陷也会显示出很长的相干时间。

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然而，碳纳米结构的量子性能仍然因为不能以原子精度改变sp2-碳晶格而受到阻碍。

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这里，我们证明拓扑裁剪在分子石墨烯纳米结构中具有优越的量子性能。我们揭示了退相干机制、量化了核效应和环境效应，并观察了超越大多数纳米材料的自旋相干时间。

这些结果验证了长期以来关于石墨烯拓扑缺陷相干行为的假设，并为在未来的碳基光电、电子和生物活性系统中引入受控量子相干中心提供了可能性。

Abstract

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Robustly coherent spin centers that can be integrated into devices are a key ingredient of quantum technologies. Vacancies in semiconductors are excellent candidates, and theory predicts that defects in conjugated carbon materials should also display long coherence times. However, the quantum performance of carbon nanostructures has remained stunted by aninability to alter the sp2-carbon lattice with atomic precision. Here, we demonstrate that topological tailoring leads to superior quantum performance in molecular graphene nanostructures. We unravel the decoherence mechanisms, quantify nuclear and environmental effects, and observe spin-coherence times that outclass most nanomaterials. These results validate long-standing assumptions on the coherent behavior of topological defects ingraphene and open up the possibility of introducing controlled quantum-coherent centers in the upcoming generation of carbon-based optoelectronic, electronic, and bioactive systems.

Fatigue-resistant high-performance elastocaloric materials made by additive manufacturing

抗疲劳高性能弹性材料的增材制造

作者：Huilong Hou, Emrah Simsek, Tao Ma, et al

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链接：

https://science.sciencemag.org/content/366/6469/1116

摘要：

弹性制冷是一种固态制冷技术，通过应力诱导相变利用释放和吸收的潜热。然而，与转换相关的滞后不利于高效的能量转换和功能耐久性。

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通过对镍钛材料的增材制造，我们研制出了热力学效率高、滞回率低的弹性降温材料。

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利用局部熔融环境和元素粉末的近共晶混合，我们在二元合金基体中形成了由富镍金属间化合物组成的纳米复合微结构。

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在准线性应力—应变行为中，微结构允许极小的迟滞—将材料效率提高了4到7倍，以及在超过100万个循环中可重复的弹性热性能。

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对弹性冷却材料实施增材制造，可以对具有长疲劳寿命的高性能金属制冷剂进行独特的微观结构控制。

Abstract

Elastocaloric cooling, a solid-state cooling technology, exploits the latent heat released and absorbed by stress-induced phase transformations. Hysteres is associated with transformation, however, is detrimental to efficient energy conversion and functional durability. We have created thermodynamically efficient, low-hysteresis elastocaloric cooling materials by means of additive manufacturing of nickel-titanium. The use of a localized molten environment and near-eutectic mixing of elemental powders has led to the formation of nanocomposite microstructures composed of a nickel-rich intermetallic compound interspersed among a binary alloy matrix. The microstructure allowed extremely small hysteresis in quasi-linear stress-strain behaviors—enhancing the materials efficiency by a factor of four to seven—and repeatable elastocaloric performance over 1 million cycles. Implementing additive manufacturing to elastocaloric cooling materials enables distinct microstructure control of high-performance metallic refrigerants with long fatigue life.

Incoherent strange metal sharply bounded by a critical doping in Bi2212

非相干奇异金属受Bi2212中一种临界掺杂约束

作者：Su-Di Chen, Makoto Hashimoto, Yu He, etal

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链接：

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https://science.sciencemag.org/content/366/6469/1099

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摘要：

在普通金属中，宏观性质通过利用准粒子的概念得以理解。在铜高温超导体中，超过最高转变温度的金属态是反常的，被称为“奇异金属”。

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我们利用角分辨光电子发射光谱学研究了这种状态。

随着在温度无关的临界值pc~ 0.19处的掺杂量增加，我们观察到在布里渊带边界附近，具有非相干谱函数特征的奇异金属突然重构为拥有准粒子的更传统的金属。

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在超导涨落温度以上，我们发现在pc值相同的情况下，赝隙也会不连续地崩塌。

这些观测结果表明，非相干奇异金属是一种独特的状态，是赝隙形成的前提；这样的发现与现有的赝隙量子临界点情景不相容。

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Abstract

In normal metals, macroscopic properties are understood using the concept of quasiparticles. In the cuprate high-temperature superconductors, the metallic state above the highest transition temperature is anomalous and is known as the “strange metal.” We studied this state using angle-resolved photoemission spectroscopy. With increasing doping across a temperature-independent critical value pc~ 0.19, we observed that near the Brillouin zone boundary, the strange metal, characterized by an incoherent spectral function, abruptly reconstructs into a more conventional metal with quasiparticles. Above the temperature of superconducting fluctuations, we found that the pseudogap also discontinuously collapses at the very same value of pcThese observations suggest that the incoherent strange metal is a distinct state and aprerequisite for the pseudogap; such findings are incompatible with existing pseudogap quantum critical point scenarios.

海洋地球物理学

Marine Geophysics

Illuminating seafloor faults and ocean dynamics with dark fiber distributed acoustic sensing

利用暗光纤分布式声传感阐明海底断层和海洋动力学

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作者：Nathaniel J. Lindsey, T. Craig Dawe, Jonathan B. Ajo-Franklin

链接：

https://science.sciencemag.org/content/366/6469/1103

摘要：

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分布式光纤传感技术与现有的海底电缆（暗光纤）相结合，可以观测海洋和固体地球现象。

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在为期4天的维护期间，我们利用来自支撑蒙特利加速研究系统的电缆光纤，以及在岸上操作的分布式声波传感（DAS）仪器，创建了一个含有约1万个组件、20公里长的地震阵列。

一个小地震波场的记录确定了多个海底断裂带。周围的噪声主要是浅滩海洋表面波，但也包括观测到的原位次生微震产生、低潮后的钻孔、风暴引起的泥沙搬运、亚重力波和破碎的内部波。

微地震带的DAS振幅跟踪了北太平洋风暴周期期间的海况动力学。这些观测结果凸显了该方法在海洋地球物理学方面的潜力。

Abstract

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Distributed fiber-optic sensing technology coupled to existing subsea cables (dark fiber) allows observation of ocean and solid earth phenomena. We used an optical fiber from the cable supporting the Monterey Accelerated Research System during a 4-day maintenance period with a distributed acoustic sensing (DAS) instrument operating onshore, creating a~10,000-component, 20-kilometer-long seismic array. Recordings of a minor earthquake wavefield identified multiple submarine fault zones. Ambient noise was dominated by shoaling ocean surface waves but also contained observations of in situ secondary microseism generation, post–low-tide bores, storm-induced sediment transport, infragravity waves, and breaking internal waves. DAS amplitudes in the microseism band tracked sea-state dynamics during a stormcycle in the northern Pacific. These observations highlight this method’s potential for marine geophysics.

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