物理与天文2016arxiv.org
实验室中制得固态金属氢
Solid metallic hydrogen has been produced in the laboratory
入门 · 约 30 分钟读完前置知识：高压物理基础、金刚石对顶砧原理
导读
哈佛大学 Silvera 团队宣称在实验室用金刚石对顶砧（DAC）将氢压缩至约 495 GPa，首次观测到固态金属氢（SMH）。论文称其可能在卸压后以亚稳态形式于室温存在，若属实且具超导性，可能对能源问题和火箭推进剂产生重大影响。
HN 关注点：固态金属氢是凝聚态物理长期追求的‘圣杯’，且论文宣称的亚稳态与超导潜力极具想象空间，HN 读者关注其技术细节与结论是否可信。
HN 评论精选
这几条评论里：支持 1 质疑 1 补充 1 亲历 1
支持惊叹论文实验工艺的精妙与‘土法’拍照的反差
论文中的实验技术细节令人惊叹：使用约 30 微米台面的 IIa 型锥形合成金刚石，用反应离子刻蚀去除表面缺陷，再高温真空退火消除残余应力；由于氧化铝可阻挡氢扩散，用原子层沉积在金刚石和铼垫片上镀了 50 纳米非晶氧化铝。压力先用红宝石荧光标定到约 88 GPa，更高压力则用傅里叶变换红外光谱仪测量氢的振动峰来定压。而实验照片竟然是用智能手机对着改装立体显微镜的目镜拍的。
twic查看英文原文
> We used type IIac conic synthetic diamonds (supplied by Almax Easy-Lab) with ~30 micron diameter culet flats. About 5 microns were etched off of the diamond culets using the technique of reactive ion etching, to remove defects from the surface. The diamonds were then vacuum annealed at high temperature to remove residual stress. Alumina is known to act as a diffusion barrier against hydrogen. The diamonds, with the mounted rhenium gasket, were coated with a 50 nm thick layer of amorphous alumina by the process of atomic layer deposition. Incredible technology! > The pressure was initially determined to ~88 GPa by ruby fluorescence using the scale of Chijioke et al (20); the exciting laser power was limited to a few mW. At higher pressures we measured the IR vibron absorption peaks of hydrogen with a Fourier transform infrared spectrometer with a thermal IR source, using the known pressure dependence of the IR vibron peaks for pressure determination (see SM). Just incredible! > Photos were taken with a smartphone camera at the ocular of a modified stereo microscope ...
补充摘录论文关键结论：亚稳态、超导潜力与样品保存状态
论文里有不少值得引用的句子：SMH 被预测为亚稳态，卸压后可能在室温下存在；若如此且具超导性，可能对人类能源问题产生重要影响，并作为强力火箭推进剂革新火箭技术。实现所需压力的主要限制是金刚石的失效。样品在 15 K 低温下装载，并放入一粒红宝石用于测压。截至撰写本文时，第一份固态金属氢样品仍保存在液氮温度的低温恒温器中。
toufka查看英文原文
Super cool stuff! There are some greatly quotable sentences in the paper: > Moreover, SMH (solid metal hydrogen) is predicted to be metastable so that it may exist at room temperature when the pressure is released. If so, and superconducting, it could have an important impact on mankind’s energy problems and would revolutionize rocketry as a powerful rocket propellant. > The principal limitation for achieving the required pressures to observe SMH in a DAC (diamond anvil cell) has been failure of the diamonds. > The sample was cryogenically loaded at 15 K and included a grain of ruby for pressure determination. > As of the writing of this article we are maintaining the first sample of the first element in the form of solid metallic hydrogen at liquid nitrogen temperature in a cryostat.
质疑提醒该领域竞争激烈、金属化判定存在争议
补充背景：arXiv 论文发表前两个月，Science News 有一篇关于金属氢制备竞争史的长文。Silvera 的团队此前把氢压到几乎不透明但无反射性——还差一点才是金属，他认为自己‘刚好低于所需压力’。而 Silvera 质疑竞争对手 Eremets 的金属化判断：‘他们每次看到什么变化就称之为金属，但并没有金属氢的证据。’研究者们认为这种反复争论是领域快速进展的标志，‘这是非常健康的竞争’。
npunt查看英文原文
Very exciting! For context, here's a nice long article (Aug 2016, 2 months before this arxiv paper came out) on the recent history of attempts to make it, with quotes from author of current paper and others in the field: https://www.sciencenews.org/article/pressure-make-metallic-hydrogen > A few months later, Silvera’s group squeezed hydrogen hard enough to make it nearly opaque, though not reflective — not quite a metal. “We think we’re just below the pressure that you need to make metallic hydrogen,” Silvera says. His findings are consistent with Eremets’ new phase, but Silvera disputes Eremets’ speculations of metallicity. “Every time they see something change they call it metallic,” Silvera says. “But they don’t really have evidence of metallic hydrogen.” > All this back and forth may seem chaotic, but it’s also a sign of a swiftly progressing field, the researchers say. “I think it’s very healthy competition,” Gregoryanz says. “When you realize that somebody is getting ahead of you, you work hard.”
亲历亲历者描述目睹样品的震撼感
我亲眼看到了！显微镜下一个小小的闪亮斑点，那种看到一种可以说在宇宙任何地方都从未存在过的物质形态的激动，无以言表。
InDemoVeritas查看英文原文
I saw it! A tiny, shiny speck under the microscope, and the thrill of seeing a form of matter which, it can be argued, has never existed anywhere in the universe. Ever.
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