World’s smelliest superconductor

Superconductors, if you aren’t aware,  are materials that can carry electrical current with absolutely zero electrical resistance. They could be used to make lossless energy grids, levitating transport, and even a new generation of supercomputers.

In the world of superconductors, the holy grail has always been a superconductor that works at room temperature. Typically, materials have to be supercooled in order for them to display superconductor properties. That’s not easy.

But fortunately, the room temp superconductors may now be closer to reality.

A study published online in Nature suggests that the quantum properties of hydrogen play a huge role in the ability of hydrogen sulfide to superconduct at a far higher temperature than any other material.

Last year, German researchers identified hydrogen sulphide, the stuff that makes rotten eggs smell bad, as the highest temperature superconductor yet. When subjected to high pressures, it displays superconducting behaviour at -70°C (-94°F), which is higher than any other high temperature superconductor.

Since then, scientists have been trying to discover why hydrogen sulfide can superconduct at such a high temperature. And this new study suggests that it is hydrogen’s ability to have properties of both particles and waves that gives it its enhanced superconducting abilities, as it changes the structure of the chemical bonds between atoms

Quantum properties

If you model predictions based on hydrogen’s properties as a particle, an extremely high pressure would be needed for the hydrogen sulfur bonds to be symmetrical—higher than the pressures used in the German experiment. At lower pressures, these bonds become off-centre, asymmetrical.

However, if one treats hydrogen as a wave, the pressures required to achieve superconductance is lower, near the pressure used in the German experiment. The similar values reached in the calculations of the study and the results of the German experiments suggest that this quantum symmetrisation is why hydrogen sulfide can superconduct at higher temperature.

Hydrogen sulfide at normal and high pressure Credit: Nature

Hydrogen, being the lightest element, is most susceptible to quantum properties. Many hydrogen compounds have different structural and chemical properties than expected, due to the quantum nature. In high-pressure ice, quantum fluctuations of the proton makes the chemical bonds between atoms become symmetrical.

“Theory and computation have played an important role in the hunt for superconducting hydrides under extreme compression,” said study co-author Professor Chris Pickard of Cambridge’s Department of Materials Science & Metallurgy. “The challenges for the future are twofold – increasing the temperature towards room temperature, but, more importantly, dramatically reducing the pressures required.”

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