Guang-Han Cao is a Qiushi Professor at Zhejiang University. He obtained a PhD in physics from University of Science and Technology of China in 1995. As an STA fellow, He visited National Institute for Materials Science at Tsukuba, Japan, from 1999 to 2001. He works on synthesis, structure, and physical properties of high-temperature superconductors and related materials. Some novel superconductors discovered in recent years in his group include iron-based ferromagnetic superconductors, iron-based superconductors with intergrowth structures and self doping, and quasi-one-dimensional chromium-based superconductors. He has published/coauthored over 300 papers with ∼11000 citations in Google Scholar. Currently, he is an associate editor of ‘Sci. China Materials’ and ‘J. Superconductivity and Novel Magnetism’, and on the editorial board of ‘Phys. Rev. B’ and ‘Materials’.
Cuprate and iron-based superconductors are structurally featured with two-dimensional motifs, CuO2 planes and FeAs/Se layers, which are believed to play the key role for superconductivity. Hence it is rational to explore new superconductors by the “block-layer (BL) design”, namely with intercalating various BLs into the superconducting motifs, which actually forms an intergrowth structure. However, it is not easy to evaluate the thermodynamic stability properly because of its complex structure with multiple elements involved.
In this talk, we address this particular issue with a simple BL model, employing the experimental finding of the concepts of lattice match and charge transfer between distinct BLs. We found that the inter-BL charge transfer lowers the internal energy, while lattice match minimizes the elastic energy, both of which together make an intergrowth structure stabilized. This work rationalizes the basic principles of BL design for intergrowth structures, which can be utilized not only for finding new superconducting materials but also for investigating other layered quantum materials.