Quantum Effects at Work in the World’s Smelliest Superconductor

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Researchers have found that quantum effects are the reason that hydrogen sulphide – which has the distinct smell of rotten eggs –behaves as a superconductor at record-breaking temperatures, which may aid in the search for room temperature superconductors.

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.

The quantum behaviour of hydrogen affects the structural properties of hydrogen-rich compounds, which are possible candidates for the elusive room temperature superconductor, according to new research co-authored at the University of Cambridge.

New theoretical results, published online in the journal Nature, suggest that the quantum nature of hydrogen – meaning that it can behave like a particle or a wave – strongly affects the recently discovered hydrogen sulphur superconductor, a compound that when subjected to extremely high pressure, is the highest-temperature superconductor yet identified. This new step towards understanding the underlying physics of high temperature superconductivity may aid in the search for a room temperature superconductor, which could be used for applications such as levitating trains, lossless electrical grids and next-generation supercomputers.

Superconductors are materials that carry electrical current with zero electrical resistance. Low-temperature, or conventional, superconductors were first identified in the early 20th century, but they need to be cooled close to absolute zero (zero degrees on the Kelvin scale, or -273 degrees Celsius) before they start to display superconductivity. For the past century, researchers have been searching for materials that behave as superconductors at higher temperatures, which would make them more suitable for practical applications. The ultimate goal is to identify a material which behaves as a superconductor at room temperature.

Last year, German researchers identified the highest temperature superconductor yet – hydrogen sulphide, the same compound that gives rotten eggs their distinctive odour. When subjected to extreme pressure – about one million times higher than the Earth’s atmospheric pressure – this stinky compound displays superconducting behaviour at temperatures as high as 203 Kelvin (-70 degrees Celsius), which is far higher than any other high temperature superconductor yet discovered.

Since this discovery, researchers have attempted to understand what it is about hydrogen sulphide that makes it capable of superconducting at such high temperatures. Now, new theoretical results suggest that the quantum behaviour of hydrogen may be the reason, as it changes the structure of the chemical bonds between atoms. The results were obtained by an international collaboration of researchers led by the University of the Basque Country and the Donostia International Physics Center, and including researchers from the University of Cambridge.

The behaviour of objects in our daily life is governed by classical, or Newtonian, physics. If an object is moving, we can measure both its position and momentum, to determine where an object is going and how long it will take to get there. The two properties are inherently linked.

However, in the strange world of quantum physics, things are different. According to a rule known as Heisenberg’s uncertainty principle, in any situation in which a particle has two linked properties, only one can be measured and the other must be uncertain.Page 1 of 2

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