Top > Research results > A pioneer of non-conventional superconductivity, electronic state revealed after 38 years

2017/6/29

A pioneer of non-conventional superconductivity, electronic state revealed after 38 years

University Journal Online Editorial Department

　A "superconducting state" that develops when a specific substance is cooled to a very low temperature.It is a phenomenon that shows the characteristic of complete anti-magnetism in which the electric resistance suddenly becomes zero and the magnetic field from the outside is excluded.In recent years, it has been confirmed that superconductivity is realized even in a substance group called "strongly correlated electron system" in which strong correlation between electrons works, and it is called "non-conventional superconductivity".Research groups such as the University of Tokyo and Kyoto University have revealed the electronic states of CeCu2Si2 (Ce: cerium, Cu: copper, Si: silicon), which has become the "pioneer" of non-conventional superconductivity.

　In non-conventional superconductors, many unprecedented discoveries have been made, such as "high-temperature superconductivity" that is realized at a higher temperature than conventional superconductivity.The pioneer of this was CeCu1979Si2, which was discovered in 2 to be superconducting while being a kind of "heavy fermion system" of strongly correlated electron systems.

　It has been believed that in this material, superconductivity is realized by the mediation of magnetic fluctuations.The electronic state of superconducting electrons has a symmetry of "s-wave type" in conventional metal superconductors, whereas it has a symmetry of "d-wave type" in superconductors originating from a magnetic mechanism. Expected to show.Therefore, CeCu2Si2 has also been considered to have a "d-wave" electronic state.

　This time, the research group investigated two properties, "superconducting gap structure" and "impurity effect", in order to clarify the electronic state of CeCu2Si2.As a result, it became clear that CeCu2Si2 is not "d wave type" but "s wave type".

　This result suggests that a mechanism different from the magnetic origin is involved in the "heavy fermion system", which has been thought to realize superconductivity by magnetic fluctuation.This is expected to provide new guidelines for the study of superconductivity in strongly correlated electron systems.

Paper information:[Science Advances] Fully gapped superconductivity with no sign change in the prototypical heavy-fermion CeCu2Si2 (English)

Tokyo University

Established in the 10th year of the Meiji era.A university with the longest history in Japan and at the forefront of Japanese knowledge

The University of Tokyo was established in 1877 (Meiji 10) by integrating the Tokyo Kaisei School and the Tokyo Medical School.Since its establishment, it has developed education and research in a unique way in the world as a leading university in Japan and an academic center for the fusion of East and West cultures.As a result, many human resources have been produced in a wide range of fields, and many research achievements […]

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Kyoto University

Foster a free academic style based on the spirit of "self-respect for self-weight" and open up a world of creative learning.

With the motto of self-study, we will continue to maintain a free academic style that is not bound by common sense, and develop human resources who have both creativity and practical ability.We provide an inclusive learning space that allows for diverse and hierarchical choices so that students themselves can choose a solid future through valuable trial and error. […]

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