Posted in | Quantum Physics

Scientists Resolve Thermoelectric ‘Paradox’ in Superconducting Materials

A problem that has been taxing scientists for nearly 40 years has been solved by a team of physicists at Royal Holloway, University of London.

In the 1970s, scientists made a theoretical breakthrough when they predicted that measurable thermoelectric magnetic flux would be generated in loops made of superconducting material. However, a major crisis developed when the experiments began to show paradoxical discrepancies with the theory by up to several orders of magnitude. The results of the experiments were also in disagreement with each other, leading some scientists to believe the theory was incomplete.

By taking advantage of the improvement in nanofabrication technologies over the last 30 years the team from the Department of Physics, led by Professor Victor Petrashov, was able to design and fabricate microscopic sized, bimetallic superconducting loops. The loops significantly reduced the spurious errors reported in previous experiments as they were able to trap the Earth's magnetic field, preventing it from masking the genuine thermoelectric magnetic effects which had caused problems in previous experiments.

The team used a novel Hybrid Quantum Interference Device (HyQUID), developed at Royal Holloway, which worked as an ultra-sensitive magnetometer, allowing the team to get highly accurate measurements of the magnetic effects.

The team discovered that the flaw in the original theory was that it only concentrated on the so called quasiparticle component of thermoelectric current and didn't attempt to calculate the most important circulating superconducting component.

Professor Victor Petrashov, said: “It was important to solve such a paradox as whilst standing it remained a significant unresolved piece of fundamental science

The resolution of the problem will stimulate further investigation of the fundamental aspects of thermoelectricity in superconductors opening up prospects for exploration of novel ‘giant’ thermoelectric effects which have been predicted recently. The new ‘giant’ effects may become a base for ultrasensitive bolometers which are used for detecting cosmic radiation in space.”

The research is published on 26 February in Science Advances.


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