Jan
27

A force that guides the electrons is revealed

A team of researchers led by Professor Louis Taillefer from Université de Sherbrooke, has solved a 10 years long mystery on the behavior of electrons in superconducting materials at high temperatures. In the pseudogap phase, electrons are orientated spontaneously in a preferred direction. This fundamental discovery, published in the Nature journal, removes a major obstacle to the development of superconducting materials.

Superconductors are materials that conduct electricity without resistance. They are extremely promising in terms of technology, particularly for the transport of energy, maglev trains, magnetic medical imaging, wireless communications, quantum computing and many other applications.

A new trail to superconducting materials at room temperature

The team from the Department of Physics, conducted an experiment that demonstrates the existence of an electronic state whose properties differ according to the relevant direction (anisotropy) in the pseudogap phase. “We saw the breaking of rotational symmetry. This reveals the presence of a microscopic force, which guides the electrons and could be at the origin of superconductivity, “says Professor Louis Taillefer.

In understanding these materials, this advance opens a new avenue to develop superconducting materials that could one day operate at room temperature whereas at present they must be cooled to temperatures below -100°C, which requires massive heat systems.

Louis Taillefer describes the behavior of electrons in this phase by analogy with the audience during a concert in the open air: “Before the scene is lit, the audience is dispersed in the field and oriented in all directions. When the stage lights, each viewer turns to the scene. There is then the appearance of a bias in the crowd spontaneously and collectively adopted without seats to enforce it.”

To observe this preferential orientation of the electronic phase pseudogap, the Sherbrooke team measured the Nernst effect in superconducting crystals of high purity prepared by a team from the University of British Columbia. “We have placed two opposite faces of the crystal at different temperatures,” explains Professor Taillefer. This temperature difference (thermal gradient) then generated a movement of electrons, and we’ve added a perpendicular magnetic field which bends the trajectory of electrons and can measure a transverse voltage. The Nernst effect is the ratio of voltage on the thermal gradient. This measure in one direction was very different to the same measure in the perpendicular direction, which proved that there is a preferred direction within the material, “says the researcher.

Source: original article

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