[论文解读] Direct Meissner Effect Observation of Superconductivity in Compressed H2S

Xiaoli Huang, Xin Wang+8 more|arXiv (Cornell University)|Oct 9, 2016

High-pressure geophysics and materials参考文献 28被引用 23

一句话总结

本研究首次在高压下直接观测到氢化硫（H2S）中的迈斯纳效应，证实其在149 GPa压力下具有183 K的临界温度（Tc）的超导性。通过原位交流磁化率测量，作者在117 GPa处观察到超导性的急剧转变，验证了理论预测，并确立了H2S作为氢富集氢化物中的高Tc超导体。

ABSTRACT

Recently, an extremely high superconducting temperature (Tc) of ~200 K has been reported in the sulfur hydride system above 100 GPa. This result is supported by theoretical predictions and verified experimentally. The crystal structure of the superconducting phase was also identified experimentally, confirming the theoretically predicted structure as well as a decomposition mechanism from H2S to H3S+S. Even though nuclear resonant scattering has been successfully used to provide magnetic evidence for a superconducting state, a direct measurement of the important Meissner effect is still lacking. Here we report in situ alternating-current magnetic susceptibility measurements on compressed H2S under high pressures. It is shown that superconductivity suddenly appears at 117 GPa and that Tc reaches 183 K at 149 GPa before decreasing monotonically with a further increase in pressure. This evolution agrees with both theoretical calculations and earlier experimental measurements. The idea of conventional high temperature superconductivity in hydrogen-dominant compounds has thus been realized in the sulfur hydride system under hydrostatic pressure, opening further exciting perspectives for possibly realizing room temperature superconductivity in hydrogen-based compounds.

研究动机与目标

• 为压缩H2S中的迈斯纳效应提供直接实验证据，这是超导性的关键特征。
• 解决长期以来在高压H2S中缺乏直接磁性证据支持超导性的问题，尽管已有强烈的理论和结构支持。
• 测量超导转变温度（Tc）随静水压增加的演化行为。
• 确认由高压下H2S分解形成的H3S相的稳定性和超导性质。

提出的方法

• 在立方砧压机中对H2S样品施加高达150 GPa的压力，进行原位交流磁化率测量。
• 采用氦基压力介质进行高压实验，以确保静水条件。
• 监测磁响应随温度和压力的变化，以检测抗磁屏蔽的起始，这是迈斯纳效应的特征。
• 从交流磁化率数据中抗磁信号的起始点提取超导转变温度（Tc）。
• 将实验结果与理论预测以及先前关于H2S和H3S的实验数据进行比较。

实验结果

研究问题

• RQ1 压缩H2S是否表现出直接迈斯纳效应，从而在间接证据之外确认超导性？
• RQ2 在静水压缩下，H2S中超导转变的精确压力与温度依赖关系如何？
• RQ3 观测到的Tc与氢富集氢化物的理论预测相比如何？
• RQ4 H2S中的超导相是否与理论预测及先前实验中观察到的H3S结构一致？

主要发现

• 在压缩H2S中直接观测到迈斯纳效应，抗磁响应在117 GPa处出现急剧起始。
• 超导转变温度（Tc）在149 GPa时达到最大值183 K，随后随压力进一步增加而下降。
• 观测到的Tc演化行为与理论计算以及先前关于H2S的实验结果一致。
• 超导相与H3S结构一致，该结构由高压下H2S的分解形成。
• 结果证实，在高压下，以氢为主的化合物中的常规超导性可实现极高的Tc。
• 本研究为未来探索基于氢材料的室温超导性设立了关键基准。