Interlayer Be-B bonding enhanced superconductivity driven by van Hove singularity and flat band in the t-BeB3 bilayer

Abstract

Metal-doped borophenes offer a versatile platform for realizing topological superconductivity and investigating exotic quantum states. In this study, through extensive structural searches, we identify the t-BeB3 monolayer and its stacked bilayer as the lowest-energy configurations within their respective layered systems. Compared to the monolayer, the AB′′-stacked bilayer forms interlayer Be-B covalent bonds that not only enhance thermodynamic stability but also drive a topological phase transition—resulting in the emergence of Dirac points and topological surface states near the Fermi level. Remarkably, the pz electrons localized on the interlayer Be-B bonds induce van Hove singularities and a flat band, which strongly couple to out-of-plane phonon modes. This leads to a significant enhancement in electron-phonon coupling (EPC) strength—from 0.51 in the t-BeB3 monolayer to 0.85 in the bilayer—and yields a threefold increase in the superconducting critical temperature (Tc) from 10.3 to 30.2 K. These results highlight the pivotal role of interlayer bonding in tuning the electronic structure and EPC in borophene-based materials, offering a promising pathway toward the design of high-Tc topological superconductors.

Source-reported materials — not catalogue approval

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