Coexistence of topology and superconductivity in two-dimensional anti-van't Hoff/Le Bel bonded BeC3 monolayer

Abstract

Two-dimensional topological superconductors combining nontrivial band topology with robust superconductivity remain rare in light-element systems. Here, we predict a thermodynamically stable BeC3 monolayer simultaneously hosting a symmetry-protected Dirac nodal-line ring and phonon-mediated superconductivity (Tc∼12.7 K). The structure features planar hexacoordinate beryllium atoms—an “anti-van't Hoff/Le Bel” geometry that defies classical coordination principles—with dual functionality: substantial charge transfer (1.65 e/Be) stabilizes extended carbon π networks forming the Dirac nodal ring, while low-frequency out-of-plane Be vibrations (69.8% phonon contribution) drive strong electron–phonon coupling (λ=0.68) through carbon pz states at the Fermi level. Exceptional stability (up to 2400 K, cohesive energy 6.44 eV/atom) establishes BeC3 as a viable experimental target. Beyond identifying a promising topological superconductor, this work highlights the functional importance of planar hypercoordinate motifs in realizing exceptional quantum properties.