BiS₂-based layered superconductor Bi₄O ₄S₃

Exotic superconductivity has often been discovered in materials with a layered (two-dimensional) crystal structure. The low dimensionality can affect the electronic structure and can realize high transition temperatures (T _c) and/or unconventional superconductivity mechanisms. We show superconductivity in a new bismuth-oxysulfide compound Bi₄O ₄S₃. Crystal structure analysis indicates that this superconductor has a layered structure composed of a stacking of spacer layers and BiS₂ layers. Band calculation suggests that the Fermi level for Bi₄O₄S₃ is just on the peak position of the partial density of states of the Bi 6p orbital within the BiS₂ layer. The BiS₂ layer will be a basic structure which provides another universality class for a layered superconducting family, and this opens up a new field in the physics and chemistry of low-dimensional superconductors.