Japanese researchers discover electron ‘saddle loops’ to enhance superconductivity

A collaborative research group involving Tohoku University, Osaka University, and several other Japanese institutions has discovered a unique electronic state known as a ‘saddle loop’ in the superconducting alloy Pt(Bi1-xSex)2.

While previous research on enhancing superconductivity through electronic ‘singularities’ (saddle points) was largely limited to 2D materials, this discovery demonstrates that these points can be connected into a ring-like structure within 3D crystals. The researchers found that as this saddle loop approaches the Fermi level, the superconducting transition temperature increases. This finding provides a new design principle for discovering high-temperature superconductors and other strongly correlated quantum materials.

In a separate development, researchers from Ibaraki University, Kitasato University, NIMS, and Hokkaido University have successfully combined circularly polarized electroluminescence (CPEL) with spin-polarized carrier transport. By adding 10% chiral molecules to an emissive polymer material, the team achieved high spin polarization of approximately 70%. This breakthrough suggests a path toward developing new devices that integrate light and spin properties.