# Room-temperature superconductivity in a carbonaceous sulfur hydride

## Abstract

One of the long-standing challenges in experimental physics is the observation of room-temperature superconductivity1,2. Recently, high-temperature conventional superconductivity in hydrogen-rich materials has been reported in several systems under high pressure3,4,5. An  important discovery leading to room-temperature superconductivity is the pressure-driven disproportionation of hydrogen sulfide (H2S) to H3S, with a confirmed transition temperature of 203 kelvin at 155 gigapascals3,6. Both H2S and CH4 readily mix with hydrogen to form guest–host structures at lower pressures7, and are of  comparable size at 4 gigapascals. By introducing methane at low pressures into the H2S + H2 precursor mixture for H3S, molecular exchange is allowed within a large assemblage of van der Waals solids that are hydrogen-rich with H2 inclusions; these guest–host structures become the building blocks of superconducting compounds at extreme conditions. Here we report superconductivity in a photochemically transformed carbonaceous sulfur hydride system, starting from elemental precursors, with a maximum superconducting transition temperature of 287.7 ± 1.2 kelvin (about 15 degrees Celsius) achieved at 267 ± 10 gigapascals. The superconducting state is observed over a broad pressure range in the diamond anvil cell, from 140 to 275 gigapascals, with a sharp upturn in transition temperature above 220 gigapascals. Superconductivity is established by the observation of zero resistance, a magnetic susceptibility of up to 190 gigapascals, and reduction of the transition temperature under an external magnetic field of up to 9 tesla, with an upper critical magnetic field of about 62 tesla according to the Ginzburg–Landau model at zero temperature. The light, quantum nature of hydrogen limits the structural and stoichiometric determination of the system by X-ray scattering techniques, but Raman spectroscopy is used to probe the chemical and structural transformations before metallization. The introduction of chemical tuning within our ternary system could enable the preservation of the properties of room-temperature superconductivity at lower pressures.

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## Data availability

The data supporting the findings of this study are available within the article and its Supplementary Information files, and from the corresponding author upon reasonable request.

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## Acknowledgements

We thank N. Meyers for technical support during the initial stage of the project. Also, we thank L. Koelbl for discussions on the manuscript. Preparation of diamond surfaces was performed in part at the University of Rochester Integrated Nanosystems Center. This research was supported by NSF (grant number DMR-1809649) and the DOE Stockpile Stewardship Academic Alliance Program (grant number DE-NA0003898). This work supported by the US Department of Energy, Office of Science, Fusion Energy Sciences under award number DE-SC0020340. A.S. and K.V.L. are supported by DE-SC0020303.

## Author information

Authors

### Contributions

E.S., N.D.-G. and R.M. performed the Raman and electrical conductivity measurements and contributed to the writing of the paper; K.V. participated in the Raman measurements and analysis of the Raman data. H.V. analysed the low-temperature magnetic-field-dependent electrical conductivity measurements and contributed to the writing of the paper. M.D. provided technical support during the initial stage of the electrical conductivity measurements, performed magnetic susceptibility measurements and contributed to the writing of the paper. R.P.D. conceived the project and performed electrical conductivity and magnetic susceptibility experiments. K.V.L. and A.S. analysed the data and the chemistry protocol. K.V.L., A.S. and R.P.D. wrote the paper. All authors discussed the results and commented on the manuscript.

### Corresponding author

Correspondence to Ranga P. Dias.

## Ethics declarations

### Competing interests

The authors declare no competing interests.

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## Extended data figures and tables

### Extended Data Fig. 1 Vibrational frequencies of the C–S–H sample.

Pressure versus Raman shift for low-frequency modes compared to pure sulfur modes. Grey solid markers are from the sample; the green, red and blue crosses represent different phases of pure sulfur.

### Extended Data Fig. 2 Raman spectra of the C–S–H sample.

Spectral deconvolution of Raman spectra of the C–S–H compound used to find the peak positions reported in Fig. 3b. a.u., arbitrary units.

### Extended Data Fig. 3 Superconducting properties of the C–S–H system.

a, Coherence length versus temperature. b, Temperature dependence of the penetration depth. The penetration depth can be determined to be λ(0) > 3.8 nm as $$\lambda (0)={\varphi }_{0}/[2\sqrt{2}{\rm{\pi }}{H}_{{\rm{c}}}(0)\xi (0)]\,$$ with Hc(0) = 61.8 T and ξ(0) = 2.3 nm; ϕ0 is the magnetic flux quantum. c, GL parameter, κ = λ(T)/ξ(T) at $$T=0$$; $$\kappa > 1/\sqrt{2}$$ indicates type II superconductivity. In our experiment κ > 1.1, so the sample can be identified as a type II superconductor. d, Variation of the superconducting bandgap Δ versus temperature, $$\varDelta (T)/\varDelta (0)=1.76{k}_{{\rm{B}}}\,{T}_{{\rm{c}}}\sqrt{1-(T/{T}_{{\rm{c}}})}$$ (kB, Boltzmann constant).

### Extended Data Fig. 4 Superconducting transition at 272 GPa.

Temperature-dependent quasi-four-point electric resistance measurement of the C–S–H sample at 272 GPa, showing the superconducting transitions at ~280 K. Tc was determined from the onset of superconductivity (see arrow). A superconducting step is observed at the transition midpoint.

### Extended Data Fig. 5 A DFT-optimized structure for (H2S)2H2 at 4 GPa.

View along the (00−1) (left) and (–100) (right) planes of a calculated snapshot of (H2S)2H2. S–H distances between 1.4 Å and 2.8 Å are shown as dashed lines to indicate potential hydrogen bonds.

### Extended Data Fig. 6 A DFT-optimized structure for (H2S)(CH4)H2 (variant 2) at 4 GPa.

View along the (00−1) (left) and (−100) (right) planes of a calculated snapshot of a variant (number 2) of (H2S)(CH4)H2. S–H distances between 1.4 Å and 2.8 Å are shown as dashed lines to indicate potential hydrogen bonds.

### Extended Data Fig. 7 Additional data on superconducting transition and pressure measurements.

a, Representative spectra of the diamond Raman edge used for pressure determination. b, Plot of resistance versus temperature, showing that the width of the superconducting drop is less than 1 K. Inset, zoom-in of the resistance near 0 Ω. c, Temperature dependence of the resistance of C–S–H at different pressures (different samples). d, Temperature dependence of the measured a.c. susceptibility of C–S–H at 182 GPa. The inset shows raw data at 138 GPa.

## Supplementary information

### Supplementary Information

This file contains Supplementary Tables 1-4.

### Video 1

Photochemical synthesis of C-S-H system. The video shows the sample chamber inside of a diamond anvil cell, looking axially through the top diamond. The sample originally exists of carbon and sulfur, shown as a black powder, sitting inside a hydrogen-rich environment. The sample is at 4 GPa and is illuminated by 10 mW of 532 nm of laser light for several minutes to initiate and take to completion the photochemical reaction to produce a CSH Van der Waals solid. This sample can be seen to be grown with a single crystal-like motif.

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Snider, E., Dasenbrock-Gammon, N., McBride, R. et al. Room-temperature superconductivity in a carbonaceous sulfur hydride. Nature 586, 373–377 (2020). https://doi.org/10.1038/s41586-020-2801-z

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• ### First room-temperature superconductor excites â and baffles â scientists

• Davide Castelvecchi

Nature (2020)