Carbonaceous sulfur hydride
Identifiers
Properties
CH8S
Molar mass 52.14 g·mol−1
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

Carbonaceous sulfur hydride (CSH) is a purported room-temperature superconductor[1] that was announced in October 2020.[2] The material is claimed to have a maximal superconducting transition temperature of 15 °C (59 °F) at a pressure of 267 gigapascals (GPa), though the validity of the claim has faced criticism.[3][4][5][6][7] In September 2022 the article was retracted by Nature due to a non standard, user-defined data analysis calling into question the scientific validity of the claim.[8] In July 2023 a second paper by the author was retracted from Physical Review Letters due to suspected data fabrication.

267 GPa corresponds to a pressure equivalent to three quarters of the pressure at the center of the Earth.[9] The material is an uncharacterized ternary polyhydride compound of carbon, sulfur and hydrogen with a chemical formula that is thought to be CH8S. Measurements under extreme pressure are difficult, and in particular the elements are too light for an X-ray determination of crystal structure (X-ray crystallography).[2] This would be the closest to room temperature achieved for a superconductor, with an onset almost 30 °C higher than that of the previous record-holder.[10]

Background

Main article: Room-temperature superconductor

Prior to 1911, all known electrical conductors exhibited electrical resistance, due to collisions of the charge carrier with atoms in the material. Researchers discovered that in certain materials at low temperatures, the charge carriers interact with phonons in the material and form Cooper pairs, as described by BCS theory. This process results in the formation of a superconductor, with zero electrical resistance. During the transition to the superconducting state, the magnetic field lines are expelled from the interior of the material, which allows for the possibility of magnetic levitation. The effect has historically been known to occur at only low temperatures, but researchers have spent decades attempting to find a material that could operate at room temperature.[11]

Synthesis

The material is a ternary polyhydride compound of carbon, sulfur and hydrogen with a chemical formula that is thought to be CSH8. As of October 2020, the material's molecular structure remains uncharacterized, as extreme pressures and the light elements used are unsuitable for most measurements, such as X-ray determination.[2]

The material was reportedly synthesized by compressing methane (CH4), hydrogen sulfide (H2S) and hydrogen (H2) in a diamond anvil cell and illuminating with a 532 nm green laser.[2] A starting compound of carbon and sulfur is synthesized with a 1:1 molar ratio, formed into balls less than five microns in diameter, and placed into a diamond anvil cell. Hydrogen gas is then added and the system is compressed to 4.0 GPa and illuminated with a 532-nm laser for several hours. It was reported that the crystal is not stable under 10 GPa and can be destroyed if left at room temperature overnight.[2] Other researchers were skeptical that such materials could serve as room temperature superconductors, as the absence of van Hove singularities or similar peaks in the electronic density of states of more than 3000 candidate phases rules out conventional superconductivity.[12]

Superconductivity

Superconductivity for sulfur hydrides without carbon was first reported in 2015.[13]

On 14 October 2020, a paper by Ranga P. Dias, et al. was published claiming that carbonaceous sulfur hydride is the world's first room-temperature superconductor.[2] The report received significant media coverage.[9][14][15][16][17][11][18] On 26 September 2022 this paper was retracted.[19][20] A superconducting state was claimed at temperatures as high as 15 °C (59 °F).[21][22] This would have set a new record for high-temperature superconductivity, with a transition temperature almost 30 °C (54 °F) higher than the previous record holder.[10] With a reported superconducting transition of 15 °C, it would be the first material known which does not have to be cooled to enter a superconducting phase.[9] Despite the enormous advancement, the superconducting state was claimed to be observable only at the very high pressure of 267 GPa (38.7 million psi), which is about a million times higher than the pressure in a typical car tire.[22]

The highest superconducting transition temperature reported was 287.7 ± 1.2 K (14.6 ± 1.2 °C; 58.2 ± 2.2 °F) at a pressure of 267 ± 10 GPa (38.7 ± 1.5 million psi). The material was tested at several lower pressures, and it was reported that at 138 ± 7 GPa (20.0 ± 1.0 million psi), the transition temperature is lowered to 147 K (−126 °C; −195 °F).[2] In addition, as expected from BCS theory, a notable decrease in the transition temperature was reported when an external magnetic field is applied. The scientists reported that the transition temperature was lowered by 22 K (40 °F) in a nine-tesla magnetic field at a pressure of 267 GPa.[2]

Criticism

The validity of these results was called into question[3] by Jorge E. Hirsch[4] as well as others.[7][5] Unavailability of the data prompted an editor's note on the original paper.[2] The criticism focuses on the measurements of AC susceptibility[6] [23] used to test the superconductivity as the more definitive Meissner effect is too hard to observe at the scale of the experiments; nevertheless this effect has been measured later on sulfur hydrides without carbon by another team[24] but those results have also been called into question.[25]

On February 15, 2022, Nature added the following Editor's Note to the article reporting room temperature superconductivity in carbonaceous sulfur hydride:

"The editors of Nature have been alerted to concerns regarding the manner in which the data in this paper have been processed and interpreted. Nature is working with the authors to investigate these concerns and establish what (if any) impact they will have on the paper’s results and conclusions. In the meantime, readers are advised to use caution when using results reported therein."[2]

On 26 September 26, 2022, the original article by Snider et al. was retracted by Nature.[2][8]

References

  1. ^ The technical term "room-temperature superconductor" means temperatures as low as the melting point of ice, rather than typical room temperatures.
  2. ^ a b c d e f g h i j k Snider, Elliot; Dasenbrock-Gammon, Nathan; McBride, Raymond; Debessai, Mathew; Vindana, Hiranya; Vencatasamy, Kevin; Lawler, Keith V.; Salamat, Ashkan; Dias, Ranga P. (15 October 2020). "RETRACTED ARTICLE: Room-temperature superconductivity in a carbonaceous sulfur hydride". Nature. 586 (7829): 373–377. Bibcode:2020Natur.586..373S. doi:10.1038/s41586-020-2801-z. OSTI 1673473. PMID 33057222. S2CID 222823227.
  3. ^ a b "Breakthrough or bust? Claim of room-temperature superconductivity draws fire". Retrieved 2021-10-26.
  4. ^ a b Hirsch, J. E.; Marsiglio, F. (August 2021). "Unusual width of the superconducting transition in a hydride". Nature. 596 (7873): E9–E10. arXiv:2010.10307. Bibcode:2021Natur.596E...9H. doi:10.1038/s41586-021-03595-z. ISSN 1476-4687. PMID 34433940. S2CID 237306217.
  5. ^ a b Eremets, M. I.; Minkov, V. S.; Drozdov, A. P.; Kong, P. P.; Ksenofontov, V.; Shylin, S. I.; Bud’ko, S. L.; Prozorov, R.; Balakirev, F. F.; Sun, Dan; Mozaffari, S. (2022-03-25). "High-Temperature Superconductivity in Hydrides: Experimental Evidence and Details". Journal of Superconductivity and Novel Magnetism. 35 (4): 965–977. arXiv:2201.05137. doi:10.1007/s10948-022-06148-1. ISSN 1557-1939. S2CID 245906117.
  6. ^ a b Hirsch, J. E. (2021-09-26). "On the ac magnetic susceptibility of a room temperature superconductor: anatomy of a probable scientific fraud". Physica C: Superconductivity and Its Applications: 1353964. arXiv:2110.12854. doi:10.1016/j.physc.2021.1353964. ISSN 0921-4534. S2CID 239194714.
  7. ^ a b Dogan, Mehmet; Cohen, Marvin L. (2021-04-15). "Anomalous behavior in high-pressure carbonaceous sulfur hydride". Physica C: Superconductivity and Its Applications. 583: 1353851. arXiv:2012.10771. Bibcode:2021PhyC..58353851D. doi:10.1016/j.physc.2021.1353851. ISSN 0921-4534. S2CID 229340504.
  8. ^ a b Castelvecchi, Davide (2022-09-27). "Room-Stunning room-temperature-superconductor claim is retracted". Nature. doi:10.1038/d41586-022-03066-z. PMID 36171305. S2CID 252597663.
  9. ^ a b c Service, Robert F. (2020-10-16). "At last, room temperature superconductivity achieved". Science. 370 (6514): 273–274. Bibcode:2020Sci...370..273S. doi:10.1126/science.370.6514.273. ISSN 0036-8075. PMID 33060340. S2CID 222841128.
  10. ^ a b "Material sets superconducting record". Chemical & Engineering News. Retrieved 2020-10-17.
  11. ^ a b Wood, Charlie (14 October 2020). "Room-Temperature Superconductivity Achieved for the First Time". Quanta Magazine. Retrieved 2020-10-16.
  12. ^ Gubler, Moritz; Flores-Livas, José A.; Kozhevnikov, Anton; Goedecker, Stefan (2022-01-06). "Missing theoretical evidence for conventional room-temperature superconductivity in low-enthalpy structures of carbonaceous sulfur hydrides". Physical Review Materials. 6 (1): 014801. arXiv:2109.10019. Bibcode:2022PhRvM...6a4801G. doi:10.1103/PhysRevMaterials.6.014801. ISSN 2475-9953. S2CID 237581517.
  13. ^ Cartlidge, Edwin (2015). "Superconductivity record sparks wave of follow-up physics". Nature. 524 (7565): 277. Bibcode:2015Natur.524..277C. doi:10.1038/nature.2015.18191. PMID 26289188. S2CID 2294273.
  14. ^ Castelvecchi, Davide (15 October 2020). "First room-temperature superconductor excites — and baffles — scientists". Nature. 586 (7829): 349. Bibcode:2020Natur.586..349C. doi:10.1038/d41586-020-02895-0. PMID 33057238. S2CID 222838731.
  15. ^ Conover, Emily (2020-10-14). "The first room-temperature superconductor has finally been found". Science News. Retrieved 2020-10-16.
  16. ^ Delbert, Caroline (2020-10-15). "In a Monumental First, Scientists Discover a Room-Temperature Superconductor". Popular Mechanics. Retrieved 2020-10-16.
  17. ^ Chang, Kenneth (2020-10-14). "Finally, the First Room-Temperature Superconductor". The New York Times. ISSN 0362-4331. Retrieved 2020-10-16.
  18. ^ Rochester, University of (2020-10-14). ""Holy Grail" Sought for More Than a Century: Researchers Synthesize Room Temperature Superconducting Material". SciTechDaily. Retrieved 2020-10-16.
  19. ^ Eric Hand (26 September 2022). "'Something is seriously wrong': Room-temperature superconductivity study retracted". Science. After doubts grew, blockbuster Nature paper is withdrawn over objections of study team
  20. ^ Snider, Elliot; Dasenbrock-Gammon, Nathan; McBride, Raymond; Debessai, Mathew; Vindana, Hiranya; Vencatasamy, Kevin; Lawler, Keith V.; Salamat, Ashkan; Dias, Ranga P. (2022). "Retraction Note: Room-temperature superconductivity in a carbonaceous sulfur hydride". Nature. 610 (7933): 804. Bibcode:2022Natur.610..804S. doi:10.1038/s41586-022-05294-9. PMID 36163290. S2CID 252544156.
  21. ^ Johnston, Hamish (14 October 2020). "Superconductivity endures to 15 °C in high-pressure material". Physics World. Retrieved 15 October 2020.
  22. ^ a b Rincon, Paul (2020-10-15). "Superconductors: Material raises hope of energy revolution". BBC News. Retrieved 2020-10-16.
  23. ^ van der Marel, D.; Hirsch, J. E. (2022). "Room-temperature superconductivity – or not ? Comment on Nature 586, 373 (2020) by E. Snider et al". International Journal of Modern Physics B. 37 (4): 2375001. arXiv:2201.07686. doi:10.1142/S0217979223750012. S2CID 252324362.
  24. ^ Minkov, Vasily; Bud'ko, Sergey; Balakirev, Fedor; Prakapenka, Vitali; Chariton, Stella; Husband, Rachel; Liermann, Hanns-Peter; Eremets, Mikhail (2021-10-26). "The Meissner effect in high-temperature hydrogen-rich superconductors under high pressure". doi:10.21203/rs.3.rs-936317/v1. S2CID 244229007. ((cite journal)): Cite journal requires |journal= (help)
  25. ^ Hirsch, J. E.; Marsiglio, F. (2022). "Clear evidence against superconductivity in hydrides under high pressure". Matter and Radiation at Extremes. 7 (5): 058401. arXiv:2110.07568. doi:10.1063/5.0091404. S2CID 238857145.

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