Orbital-designed flat-band model and realization of superconductivity in three-dimensional materials

This is the authors' abstract. We don't add key points for this paper.

Electronic materials with a flat-band provide a fertile foundation for exploiting emerging quantum phenomena. Progress has been made in various two-dimensional (2D) systems, especially in a geometric frustrated kagome lattice system and a moire superlattice system for the study of unconventional superconductivity. However, intrinsic superconductivity has not yet been reported in 3D flat-band systems. The orbital degree of freedom might bring new vitality into the field of flat bands and superconductivity. Here, we propose an orbital-designed 3D flat-band model and its realization in various materials containing degenerate p-electrons, d-electrons, or molecular orbitals. More importantly, the possibility of superconductivity in some of these 3D flat-band materials, e.g., K₂Pb and K₂Bi, is revealed via first-principles calculations. Interestingly, these are intrinsically multiband superconductors. Our findings would expand the scope of flat-band studies, shedding light on the exploration of interacting effects and emerging quantum phases in 3D materials.