Shining light on superconductors

More than 20 years ago researchers in Switzerland discovered that certain materials transport electrical current without any loss. For this they need to be cooled, but because they do so at relatively high temperatures (up to -150°C) they are called high temperature superconductors. How exactly the electrons transport current in such materials is still a mystery. But the electrons can be studied using the photoelectric effect where light of high energy knocks an electron out of the material. Measuring the electrons direction and energy provides the necessary information on the motion of the electron in the material. Combining experiments at the SLS and laboratory experiments, researchers now solved a longstanding puzzle. They show that the direction of electron motion is closely related to the arrangement of the atoms in the crystal. Even small distortions of the crystal symmetry are relevant and influence the electrons motion. The solved a long standing dispute about the origin of the so called shadow band. But the search is not over yet, identifying the mechanism leading to loss less currents in these materials needs more experiments. And as in the past synchrotron light will surely be part of this search.

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