Exotic Double Sandwich Superconducting Dirac Allotrope in 2D AlB 3

Abstract The multifunctional properties of 2D AlB 3 nanosheets are systematically investigated by using crystal structure prediction, first‐principles calculations, and molecular dynamics simulations. The identified ground‐state structure, designated as AlB 3 ‐1, features a unique layered architecture consisting of two vertically stacked sandwich units that share a central borophene layer. This arrangement leads to increased mechanical strength (with an in‐plane modulus surpassing that of graphene) and excellent thermal stability (retaining integrity in ab initio molecular dynamics at 1600K). Analysis of the electronic structure revealed the presence of multiple Dirac cones near the Fermi level accompanied by linear energy dispersion and high Fermi velocities (≈10 6 m s −1 ), indicating massless charge carriers. Moderate electron–phonon coupling predicts a superconducting transition temperature of 28.84K. The structure also exhibits balanced lattice thermal conductivity (≈16.50 W m −1 K −1 ). Chemical bonding analysis indicated strong covalent B–B interactions and partially ionic Al─B bonds that contribute to the overall structural integrity. Furthermore, low‐lying allotropes (AlB 3 ‐2–10) display diverse bonding motifs and rich electronic behaviors, including metallic phases with Dirac‐like dispersions. In addition to broadening the understanding of boride‐based 2D materials, these findings highlight the potential of AlB 3 nanosheets as promising candidates for use in nanoelectronics, superconductive and thermoelectric materials, and nanoscale mechanics.