Selenium-based hetero-circulene monolayer: Coexistence of gapped Dirac fermions, heavy fermions and semiconductivity in a single quantum platform with lithium-ion battery applications

Semiconductivity, Dirac fermions, and correlated heavy fermions typically emerge in distinct material classes, such as transition metal dichalcogenides, graphene, and magic-angle twisted bilayer graphene. Integrating all three quantum features into a single platform has long been a challenge. In this study, we introduce a two-dimensional selenium-based hetero-circulene (Se-HC) monolayer composed of a carbon–selenium framework and explore its properties using density functional theory. The Se-HC monolayer exhibits dynamical, thermal, and mechanical stability. Strikingly, its electronic structure reveals a rare coexistence of gapped Dirac fermions and heavy fermions, with linearly dispersive and flat bands near the Fermi level. The Dirac cones are isotropic, with a Fermi velocity of ∼1.94 × 10 5 m/s. A narrow direct band gap separates these states by 73 meV using PBE-GGA and 0.40 eV with HSE06, enabling semiconducting behaviour without sacrificing Dirac physics. The band gap is highly tuneable via mechanical strain, compressive strain increases it, while tensile strain reduces it. We also study quasi-one-dimensional derivatives, including nanoribbons and nanotubes, and assess potential of Se-HC as a lithium-ion battery anode. This integration of semiconducting, Dirac, and flat-band features positions Se-HC as a versatile platform for quantum materials, with promising implications for next-generation electronic and energy applications. • A 2D Se-HC monolayer uniquely integrates semiconducting, Dirac fermion, and flat-band features. • Coexistence of gapped Dirac fermions and massive fermions is confirmed near the Fermi level. • The monolayer exhibits isotropic Dirac dispersion with a Fermi velocity of ∼1.94 × 10 5 m/s. • Mechanical strain enables tuneable band gaps without disrupting Dirac physics. • Se-HC nanostructures show strong potential as high-performance lithium-ion battery anodes.