Scientists at the Max Planck Institute in Mainz have directly measured the superconducting gap in hydrogen sulfide, a key step toward high-temperature superconductors. Using a novel tunneling technique under extreme pressures, they confirmed electron-phonon interactions drive the phenomenon. This breakthrough builds on discoveries from 2015 and advances the quest for room-temperature superconductivity.
Superconductors, materials that conduct electricity without resistance, hold promise for efficient power transmission and quantum computing, but most require very low temperatures. Hydrogen-rich compounds like hydrogen sulfide (H3S) have pushed boundaries, achieving superconductivity at 203 Kelvin (-70°C), far warmer than traditional ones.
For years, studying these materials was impossible due to the megabar pressures needed—over a million times atmospheric levels—ruling out standard techniques like scanning tunneling spectroscopy. Researchers at the Max Planck Institute for Chemistry in Mainz overcame this with a new planar electron tunneling spectroscopy method, allowing direct measurement of the superconducting gap in H3S for the first time.
The team found a fully open gap of about 60 millielectronvolts (meV) in H3S, compared to 44 meV in its deuterium counterpart, D3S. This difference supports theories that phonons—atomic lattice vibrations—mediate electron pairing, forming Cooper pairs that eliminate resistance.
The discovery traces back to 2015, when Mikhail Eremets' group first observed superconductivity in H3S at 203 K. Subsequent finds, like lanthanum decahydride (LaH10) at 250 K, raised hopes for room-temperature versions. Dr. Feng Du, the study's lead author, said: "We hope that by extending this tunneling technique to other hydride superconductors, the key factors that enable superconductivity at even higher temperatures can be pinpointed. This should ultimately enable the development of new materials that can operate under more practical conditions."
Eremets, who passed away in November 2024, called it "the most important work in the field of hydride superconductivity since the discovery of superconductivity in H3S in 2015." Vasily Minkov, project leader, added: "Mikhail's vision of superconductors operating at room temperature and moderate pressures comes a step closer to reality through this work."
Published in Nature (2025, volume 641, issue 8063), the findings provide crucial insights into electron interactions, potentially guiding new material designs despite the pressure challenges.
