Scientists have achieved a major milestone in the quest to understand high-temperature superconductivity in hydrogen-rich materials. Using electron tunneling spectroscopy under high pressure, the international research team led by the Max Planck Institute for Chemistry has measured the superconducting gap of H
3
S—the material that set the high-pressure superconductivity record in 2015 and serves as the parent compound for subsequent high-temperature superconducting hydrides.
The findings,
published
this week in
Nature
, provide the first direct microscopic evidence of superconductivity in hydrogen-rich materials and an important step toward its scientific understanding.
Superconductors are materials that can carry electrical current without resistance, making them invaluable for technologies such as energy transmission and storage, magnetic levitation, and quantum computing.
However, this phenomenon has usually been found well below ambient temperature, limiting widespread practical applications. The discovery of superconductivity in hydrogen-rich compounds such as hydrogen sulfide (H
3
S) which becomes superconductive at 203 Kelvin (-70° Celsius) and lanthanum decahydride (LaH
10
) reaching superconductivity at 250 Kelvin (-23° Celsius), marked a revolutionary advance towards achieving superconductivity at room temperature. Due to the transition temperature well above the boiling point of liquid nitrogen, researchers refer to high-temperature superconductors.
The key to understanding superconductivity lies in the superconducting gap—a fundamental property that reveals how electrons pair up to form the superconducting state. It is the identification of a superconducting state distinguishable from other metallic states.
Nevertheless, gauging the superconducting gap in hydrogen-rich compounds such as Hᶟ
3
Synthesizing S remains incredibly challenging. Due to the requirement for these compounds to be created in situ at extreme pressures exceeding one million times atmospheric pressure, traditional methods like scanning tunneling spectroscopy and angle-resolved photoemission spectroscopy become ineffective for measuring the gap.
The tunneling method offers a clear view into the superconducting properties of substances rich in hydrogen.
To surmount this obstacle, scientists at the Max Planck Institute in Mainz created a planar electron tunneling spectroscopy technique designed to function under these severe conditions. This breakthrough allowed them to investigate the superconducting gap in H
3
S for the first time, offering direct insight into the superconducting state of hydrogen-rich compounds.
Using this technique, the researchers discovered that H
3
S exhibits a fully open superconducting gap with a value of approximately 60 millielectron volts (meV), while its deuterium analog, D
3
S, shows a gap of about 44 meV. Deuterium is a hydrogen isotope and has one more neutron.
The fact that the gap in D
3
S is smaller than in H
3
S confirms that the interaction of electrons with phonons—quantized vibrations of the atomic lattice of a material—causes the superconducting mechanism of H
3
S, supporting long-standing theoretical predictions.
For the researchers at Mainz, this breakthrough is more than just a technical accomplishment; it also paves the way for comprehensively understanding the source of high-temperature superconductivity in materials rich with hydrogen.
“By applying this tunneling method to additional hydride superconductors, we aim to identify the crucial elements that allow for superconductivity at elevated temperatures. Achieving this could eventually lead to the creation of novel materials capable of functioning under more realistic conditions,” explains Dr. Feng Du, who authored the recently published research paper.
Dr. Mikhail Eremets, a trailblazer in high-pressure superconductivity who died in November 2024, referred to the research as “the most significant contribution to the field of hydride superconductivity since the discovery of superconductivity in hydrogen.”
3
S in 2015.”
Vasily Minkov, who leads the High-Pressure Chemistry and Physics department at the Max Planck Institute for Chemistry, remarked, “This research brings Mikhail’s idea of superconductors functioning at room temperature and modest pressures one step nearer to becoming a tangible achievement.”
More information:
Feng Du et al., The superconducting gap of HgTe
3
As determined through tunneling spectroscopy,
Nature
(2025).
DOI: 10.1038/s41586-025-08895-2
Furnished by the Max Planck Society
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