Abstract
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.
This is a preview of subscription content, access via your institution
Access options
Access Nature and 54 other Nature Portfolio journals
Get Nature+, our best-value online-access subscription
$29.99 / 30 days
cancel any time
Subscribe to this journal
Receive 12 print issues and online access
$209.00 per year
only $17.42 per issue
Rent or buy this article
Prices vary by article type
from$1.95
to$39.95
Prices may be subject to local taxes which are calculated during checkout
Similar content being viewed by others
References
Ashcroft, N. W. Metallic hydrogen: a high-temperature superconductor? Phys. Rev. Lett. 21, 1748–1749 (1968).
Richardson, C. F. & Ashcroft, N. W. High temperature superconductivity in metallic hydrogen: electron-electron enhancements. Phys. Rev. Lett. 78, 118–121 (1997).
Ashcroft, N. W. Hydrogen dominant metallic alloys: high temperature superconductors? Phys. Rev. Lett. 92, 187002 (2004).
Li, Y., Hao, J., Liu, H., Li, Y. & Ma, Y. The metallization and superconductivity of dense hydrogen sulfide. J. Chem. Phys. 140, 174712 (2014).
Drozdov, A., Eremets, M., Troyan, I., Ksenofontov, V. & Shylin, S. Conventional superconductivity at 203 Kelvin at high pressures in the sulfur hydride system. Nature 525, 73–76 (2015).
Einaga, M. et al. Crystal structure of the superconducting phase of sulfur hydride. Nat. Phys. 12, 835–838 (2016).
Duan, D. et al. Pressure-induced metallization of dense (H2S) 2H2 with high-Tc superconductivity. Sci. Rep. 4, 6968 (2014).
Errea, I. et al. High-pressure hydrogen sulfide from first principles: a strongly anharmonic phonon-mediated superconductor. Phys. Rev. Lett. 114, 157004 (2015).
Bernstein, N., Hellberg, C. S., Johannes, M., Mazin, I. & Mehl, M. What superconducts in sulfur hydrides under pressure and why. Phys. Rev. B 91, 060511 (2015).
Papaconstantopoulos, D., Klein, B., Mehl, M. & Pickett, W. Cubic H3S around 200 GPa: an atomic hydrogen superconductor stabilized by sulfur. Phys. Rev. B 91, 184511 (2015).
Flores-Livas, J. A., Sanna, A. & Gross, E. High temperature superconductivity in sulfur and selenium hydrides at high pressure. Eur. Phys. J. B 89, 1–6 (2016).
McMillan, W. & Rowell, J. Lead phonon spectrum calculated from superconducting density of states. Phys. Rev. Lett. 14, 108–112 (1965).
Carbotte, J. Properties of boson-exchange superconductors. Rev. Mod. Phys. 62, 1027 (1990).
Joyce, R. & Richards, P. Phonon contribution to the far-infrared absorptivity of superconducting and normal lead. Phys. Rev. Lett. 24, 1007 (1970).
Farnworth, B. & Timusk, T. Phonon density of states of superconducting lead. Phys. Rev. B 14, 5119–5120 (1976).
Hwang, J. & Carbotte, J. Deriving the electron–phonon spectral density of MgB2 from optical data, using maximum entropy techniques. J. Phys. Condens. Matter 26, 165702 (2014).
Carbotte, J., Timusk, T. & Hwang, J. Bosons in high-temperature superconductors: an experimental survey. Rep. Prog. Phys. 74, 066501 (2011).
Stedman, R., Almqvist, L. & Nilsson, G. Phonon-frequency distributions and heat capacities of aluminum and lead. Phys. Rev. 162, 549–557 (1967).
Perucchi, A., Baldassarre, L., Postorino, P. & Lupi, S. Optical properties across the insulator to metal transitions in vanadium oxide compounds. J. Phys. Condens. Matter 21, 323202 (2009).
Nicol, E. & Carbotte, J. Comparison of pressurized sulfur hydride with conventional superconductors. Phys. Rev. B 91, 220507 (2015).
Kamarás, K. et al. In a clean high-Tc superconductor you do not see the gap. Phys. Rev. Lett. 64, 84–87 (1990).
Errea, I. et al. Quantum hydrogen-bond symmetrization in the superconducting hydrogen sulfide system. Nature 532, 81–84 (2016).
Hofmeister, A. IR spectroscopy of alkali halides at very high pressures: Calculation of equations of state and of the response of bulk moduli to the b1-b2 phase transition. Phys. Rev. B 56, 5835–5855 (1997).
Rice, M. Organic linear conductors as systems for the study of electron-phonon interactions in the organic solid state. Phys. Rev. Lett. 37, 36–39 (1976).
Rice, M. & Choi, H.-Y. Charged-phonon absorption in doped C 60. Phys. Rev. B 45, 10173 (1992).
Kuzmenko, A. B. et al. Gate tunable infrared phonon anomalies in bilayer graphene. Phys. Rev. Lett. 103, 116804 (2009).
Eremets, M. I. Megabar high-pressure cells for Raman measurements. J. Raman Spectrosc. 34, 515–518 (2003).
Roy, P., Rouzières, M., Qi, Z. & Chubar, O. The AILES infrared beamline on the third generation synchrotron radiation facility SOLEIL. Infrared Phys. Techn. 49, 139–146 (2006).
Voute, A. et al. New high-pressure/low-temperature set-up available at the AILES beamline. Vib. Spectrosc. 86, 17–23 (2016).
Faye, M. et al. Improved mid infrared detector for high spectral or spatial resolution and synchrotron radiation use. Rev. Sci. Instrum. 87, 063119 (2016).
Acknowledgements
We thank P. Allen, D. Embury, I. Errea, F. Mauri, W. Pickett, A. Sanna and D. Tanner for helpful discussions. We also thank M. Deutsch, L. Manceron and M. Faye for useful discussions and for technical guidance. J.P.C., E.J.N. and T.T. were supported by the Natural Science and Engineering Research Council of Canada (NSERC). J.P.C. and T.T. received additional support from the Canadian Institute for Advanced Research (CIFAR). M.I.E. received financial support from the European Research Council 2010-Advanced Grant 267777. B.L. and F.C. received financial support from SOLEIL synchrotron. The high-pressure low-temperature set-up was developed through a grant from Region Centre.
Author information
Authors and Affiliations
Contributions
This project has been initiated and supervised by T.T., M.I.E. and P.R. Samples have been synthesized and characterized by A.D. and M.I.E. Infrared measurements and data treatment were carried out by B.L., F.C., J.-B.B., P.R. and T.T. The calculations were performed by E.J.N. and J.P.C. All authors contributed to the writing of the paper.
Corresponding authors
Ethics declarations
Competing interests
The authors declare no competing financial interests.
Supplementary information
Supplementary information
Supplementary information (PDF 340 kb)
Rights and permissions
About this article
Cite this article
Capitani, F., Langerome, B., Brubach, JB. et al. Spectroscopic evidence of a new energy scale for superconductivity in H3S. Nature Phys 13, 859–863 (2017). https://doi.org/10.1038/nphys4156
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1038/nphys4156
This article is cited by
-
Born effective charges and vibrational spectra in superconducting and bad conducting metals
Nature Physics (2024)
-
Full-bandwidth anisotropic Migdal-Eliashberg theory and its application to superhydrides
Communications Physics (2024)
-
On the Generalized BCS Equations Incorporating Chemical Potential for the Tc and the Calculation of the Coherence Length of Some Elements and Compressed H3S
Journal of Low Temperature Physics (2023)
-
Reply to: Absence of evidence of superconductivity in sulfur hydride in optical reflectance experiments
Nature Physics (2022)
-
Absence of evidence of superconductivity in sulfur hydride in optical reflectance experiments
Nature Physics (2022)