[论文解读] Response to critiques on Observation of the Wigner-Huntington transition to metallic hydrogen

Isaac F. Silvera, Ranga Dias|arXiv (Cornell University)|Mar 8, 2017

High-pressure geophysics and materials参考文献 2被引用 8

一句话总结

本文回应了关于在约495 GPa的金刚石对顶砧中观测到金属氢的科学批评，捍卫了从透明分子氢向光泽、反射性金属态转变的实验证据。作者反驳了关于压力标定、蓝宝石涂层作用以及反射率分析的疑虑，重申尽管在实现极端压力方面存在挑战，其金属氢检测结果依然有效。

ABSTRACT

We reported the first observation of metallic hydrogen (MH) in the low temperature limit at a pressure of ~495 GPa in an article published in Science (1). This transition was first predicted by Wigner and Huntington (WE) over 80 years ago (2) at a pressure of ~25 GPa. In recent decades it became clear that the required pressure for metallization was far greater, in the 400-500 GPa range. Until now the observation of the WE transition in diamond anvil cells (DACs) has been prevented by one problem: the diamonds break before a sufficiently high pressure has been achieved. This has driven the high-pressure community to improve DACs and experimental methods to understand and overcome the conditions that limited the performance of diamonds and the pressure. In our experiment, with increasing pressure, we observed a clear transition from a transparent sample of solid molecular hydrogen to an opaque black sample to a shiny reflective sample of MH, as determined by reflectance measurements. There is no doubt that MH was produced at the highest pressures. Yet there have been criticisms concerning the pressure that was achieved, the possibility that the 50 nm alumina layer, deposited on diamonds to inhibit diffusion of hydrogen, might be transformed to a metal and be responsible for the reflectance, and analysis of the reflectance. Here we respond to the criticisms posted on the condensed matter arXiv by Loubeyre, Occelli, and Dumas (LOD)- arXiv:1702.07192, Eremets and Drozdov (ED)- arXiv:1702.05125, and Goncharov and Struzhkin (GS)- arXiv:1702.04246.

研究动机与目标

• 回应关于在约495 GPa下观测到金属氢实验结果的科学批评。
• 为反射率测量作为Wigner-Huntington转变证据的有效性进行辩护。
• 反驳有关金刚石对顶砧尖端50 nm蓝宝石层可能产生类似金属反射率的论断。
• 澄清压力标定方法，并说明在极端条件下测量的可靠性。
• 重申尽管金刚石对顶砧存在失效限制，金属氢仍被成功制备的结论。

提出的方法

• 在金刚石对顶砧中对加压的固态分子氢进行反射率测量。
• 在金刚石对顶砧尖端使用50 nm厚的蓝宝石涂层以抑制氢扩散并防止化学反应。
• 对光学反射率数据进行详细分析，以区分金属行为与表面涂层的影响。
• 利用既定的高压标准和金刚石对顶砧性能模型重新评估压力标定。
• 通过对比数据分析和实验依据，回应Loubeyre、Occelli、Dumas、Eremets、Drozdov、Goncharov和Struzhkin的批评。

实验结果

研究问题

• RQ1 在约495 GPa下观测到的氢的光学转变是否可明确归因于金属氢的形成？
• RQ2 金刚石对顶砧尖端的50 nm蓝宝石涂层是否可能产生类似金属氢的反射率特征？
• RQ3 约495 GPa的压力是否在极端条件下得到准确标定并可重复？
• RQ4 反射率测量是否能提供金属化在氢中发生的明确证据？
• RQ5 实验观测是否与Wigner-Huntington转变的理论预测一致？

主要发现

• 随着压力增加，氢从透明到不透明再到光泽反射行为的转变被一致观测到，表明发生了向金属氢的相变。
• 反射率测量显示在高压下反射率急剧上升，与金属行为一致，且不能归因于蓝宝石涂层。
• 作者得出结论：蓝宝石层未发生金属化，因此无法解释观测到的光学特性。
• 通过既定的高压标准和多次实验的一致性，验证了压力标定的可靠性。
• 尽管在达到此类压力时存在挑战，约495 GPa处的观测转变与Wigner-Huntington转变的理论预测相符。