The discovery of a superconducting phase in sulfur hydride under high pressure with a critical temperature above 200 K has provided fresh impetus to the search for superconductors at ever higher temperatures. Although this system displays all of the hallmarks of superconductivity, the mechanism through which it arises remains to be determined. Here we provide a first optical spectroscopy study of this superconductor. Experimental results for the optical reflectivity of H₃S, under hydrostatic pressure of 150 GPa, for several temperatures and over the range 60 to 600 meV of photon energies, are compared with theoretical calculations based on Eliashberg theory. Two significant features stand out: some remarkably strong infrared-active phonons at around 160 meV, and a band with a depressed reflectance in the superconducting state in the region from 450 meV to 600 meV. In this energy range H₃S becomes more reflecting with increasing temperature, a change that is traced to superconductivity originating from the electron–phonon interaction. The shape, magnitude and energy dependence of this band at 150 K agrees with our calculations. This provides strong evidence of a conventional mechanism. However, the unusually strong optical phonon suggests a contribution of electronic degrees of freedom.

中文翻译：

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硫化氢超导新能级的光谱证据

在临界温度高于200  K的高压下在氢化硫中发现超导相，为在更高温度下寻找超导体提供了新的动力。尽管该系统显示了所有超导电性的特征，但其产生的机理尚待确定。在这里，我们提供了对该超导体的首次光谱学研究。将H ₃ S在150  GPa的静水压力下，在多个温度下以及60至600  meV的光子能量范围内的光学反射率的实验结果与基于Eliashberg理论的理论计算进行了比较。突出两个显着特征：大约160的一些非常强的红外活性声子 meV，以及在450  meV至600  meV范围内的超导状态下反射率降低的谱带。在此能量范围内，H ₃ S随着温度的升高而更多地反射，这种变化可追溯到源自电子-声子相互作用的超导性。该频带在150  K时的形状，大小和能量依赖性与我们的计算结果一致。这提供了常规机制的有力证据。然而，异常强的光学声子暗示了电子自由度的贡献。