Quantum Effects at Work in the World’s Smelliest Superconductor

Estimated reading time: 4 minutes

The researchers behind the current study believe that a similar quantum hydrogen-bond symmetrisation occurs in the hydrogen sulphide superconductor.

Theoretical models that treat hydrogen atoms as classical particles predict that at extremely high pressures – even higher than those used by the German researchers for their record-breaking superconductor – the atoms sit exactly halfway between two sulphur atoms, making a fully symmetrical structure. However, at lower pressures, hydrogen atoms move to an off-centre position, forming one shorter and one longer bond.

The researchers have found that when considering the hydrogen atoms as quantum particles behaving like waves, they form symmetrical bonds at much lower pressures – around the same as those used for the German-led experiment, meaning that quantum physics, and symmetrical hydrogen bonds, were behind the record-breaking superconductivity.

“That we are able to make quantitative predictions with such a good agreement with the experiments is exciting and means that computation can be confidently used to accelerate the discovery of high temperature superconductors,” said study co-author Professor Chris Pickard of Cambridge’s Department of Materials Science & Metallurgy.

According to the researcher’s calculations, the quantum symmetrisation of the hydrogen bond has a tremendous impact on the vibrational and superconducting properties of hydrogen sulphide. “In order to theoretically reproduce the observed pressure dependence of the superconducting critical temperature the quantum symmetrisation needs to be taken into account,” said the study’s first author, Ion Errea, from the University of the Basque Country and Donostia International Physics Center.

The discovery of such a high temperature superconductor suggests that room temperature superconductivity might be possible in other hydrogen-rich compounds. The current theoretical study shows that in all these compounds, the quantum motion of hydrogen can strongly affect the structural properties, even modifying the chemical bonding, and the electron-phonon interaction that drives the superconducting transition.

“Theory and computation have played an important role in the hunt for superconducting hydrides under extreme compression,” said Pickard. “The challenges for the future are twofold - increasing the temperature towards room temperature, but, more importantly, dramatically reducing the pressures required.”

• < Previous Page