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Nature Physics | Article Print Share/bookmark Spectroscopic evidence of a new energy scale for superconductivity in H3S F. Capitani, B. Langerome, J.-B. Brubach, P. Roy, A. Drozdov, M. I. Eremets, E. J. Nicol, J. P. Carbotte & T. Timusk Affiliations Contributions Corresponding authors Nature Physics 13, 859–863 (2017) doi:10.1038/nphys4156 Received 20 December 2016 Accepted 28 April 2017 Published online 19 June 2017 Article tools PDF Citation Rights & permissions Article metrics Abstract Abstract• Introduction• Conclusions• Methods• Additional Information• References• Acknowledgements• Author information• Supplementary information 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.