Coexistence of superconductivity and nontrivial band topology in post-transition-metal decorated bilayer kagome borophene M B 6 ( M = In , Tl )

Kagome lattice materials have attracted significant research interest due to their unique electronic structures and emergent quantum phenomena. Three-dimensional kagome systems have been extensively investigated, while the exploration of two-dimensional (2D) kagome materials remains relatively limited, presenting both scientific challenges and opportunities. In this work, through systematic first-principles calculations, $M{\mathrm{B}}_{6}$ ($M=\mathrm{In},\phantom{\rule{0.16em}{0ex}}\mathrm{Tl}$), featuring in bilayer kagome borophene, are predicted to exhibit remarkable phonon-mediated superconductivity. These two compounds display superconducting transition temperatures (${T}_{c}$) of 7.0 and 5.0 K, respectively, which are nearly two orders of magnitude higher than the 0.03 K predicted in intrinsic bilayer kagome borophene. Our analysis reveals that the coupling between B-${p}_{z}$, $M\text{\ensuremath{-}}{p}_{x}/{p}_{y}$ ($M=\mathrm{In},\phantom{\rule{0.16em}{0ex}}\mathrm{Tl}$) electrons and low-frequency phonons of metal atoms contributes greatly to their superconductivity. Notably, $M{\mathrm{B}}_{6}$ ($M=\mathrm{In},\phantom{\rule{0.16em}{0ex}}\mathrm{Tl}$) possess nontrivial band topology, suggesting the potential candidates for topological superconductivity. This work not only expands the family of 2D superconducting materials, but also provides a theoretical exploration for novel quantum phenomena in kagome systems.