Superconductors are materials that allow electrical current to flow with no resistance. This unique ability makes them extremely valuable for technologies such as efficient power transmission, energy storage, magnetic levitation systems, and quantum computers.

The challenge is that superconductivity usually occurs only at very low temperatures, far below everyday conditions. This limitation has prevented widespread practical use. That picture began to change with the discovery of superconductivity in hydrogen-rich materials. Hydrogen sulfide (H3S) becomes superconducting at 203 Kelvin (-70°Celsius), while lanthanum decahydrid (LaH10) reaches superconductivity at 250 Kelvin (-23°Celsius). These temperatures are far higher than those of earlier superconductors and are above the boiling point of liquid nitrogen, which is why scientists classify them as high temperature superconductors. Their discovery marked a major step toward the long-standing goal of room-temperature superconductivity.

The Superconducting Gap and Why It Is Crucial

At the heart of superconductivity is a feature known as the superconducting gap. This property reveals how electrons join together to form the superconducting state and serves as a clear signature that distinguishes a superconductor from an ordinary metal.

Understanding the superconducting gap is essential because it directly reflects how electrons interact inside the material. Without measuring this gap, scientists cannot fully explain why a material becomes superconducting or what mechanism makes resistance disappear.

Why Measuring Hydrogen Superconductors Is So Difficult

Despite their importance, hydrogen-rich superconductors such as H3S have been extremely challenging to study. These materials can only be created under enormous pressures that exceed atmospheric pressure by more than a million times. Because of these extreme conditions, widely used techniques like scanning tunneling spectroscopy and angle-resolved photoemission spectroscopy cannot be applied.

As a result, the superconducting gap in these materials had remained unmeasured, leaving a major gap in scientists' understanding of how high-temperature superconductivity works in hydrogen-rich compounds.

A New Tunneling Technique Breaks the Barrier

To solve this problem, researchers at the Max Planck Institute in Mainz developed a planar electron tunneling spectroscopy method that can operate under these extreme pressures. This new approach made it possible to directly probe the superconducting gap in H3S for the first time.

With this technique, the team obtained a clear picture of the superconducting state in hydrogen-rich materials, overcoming a barrier that had limited progress in the field for years.

What the Measurements Revealed