Phase Stability and Anisotropic Superconductivity in Ternary M2B4C2 (M=Ca, Mg) Monolayer
Abstract
In this work, we investigate the phase stability, electronic structure, and superconducting properties of the two-dimensional ternary borocarbides MB4C2 (M = Ca, Mg) using first-principles calculations and fully anisotropic Migdal-Eliashberg theory. Ab initio molecular dynamics, phonon dispersion, and elastic constant calculations confirm that both monolayers are dynamically, thermally, and mechanically stable. Electronic structure analysis reveals an intrinsic metallic nature with a multiband Fermi surface, where states near the Γ point are dominated by in-plane B-px, py orbitals, while zone-boundary states are primarily derived from out-of-plane B-pz orbitals. The electron-phonon coupling is determined to be λ= 0.64 for both materials, driven by the rigid covalent B-B and B-C honeycomb networks. By solving the anisotropic Eliashberg equations, we predict that CaB4C2 and MgB4C2 are nodeless two-gap superconductors with critical temperatures (Tc) of 33.4 K and 33.8 K, respectively, at a Coulomb pseudopotential of μ= 0.10. Furthermore, the superconducting state remains robust under increased Coulomb repulsion (μ= 0.13), retaining elevated Tc values of 31.2 K and 30.9 K, respectively. These findings establish MB4C2 monolayers as promising candidates for nanoscale superconducting applications and enrich the family of two-dimensional multigap superconductors.
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BibTeX
@misc{seeyangnok2026phase,
title = {{Phase Stability and Anisotropic Superconductivity in Ternary M2B4C2 (M=Ca, Mg) Monolayer}},
author = {Jakkapat Seeyangnok and Udomsilp Pinsook and Graeme J Ackland},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.19383},
eprint = {2610.19383},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.19383},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Phase Stability and Anisotropic Superconductivity in Ternary M2B4C2 (M=Ca, Mg) Monolayer
AU - Jakkapat Seeyangnok
AU - Udomsilp Pinsook
AU - Graeme J Ackland
PY - 2026
DA - 2026/10/14
PB - arXiv
DO - 10.48550/arxiv.2610.19383
UR - https://arxiv.org/abs/2610.19383
AB - In this work, we investigate the phase stability, electronic structure, and superconducting properties of the two-dimensional ternary borocarbides MB_4C_2 (M = Ca, Mg) using first-principles calculations and fully anisotropic Migdal-Eliashberg theory. Ab initio molecular dynamics, phonon dispersion, and elastic constant calculations confirm that both monolayers are dynamically, thermally, and mechanically stable. Electronic structure analysis reveals an intrinsic metallic nature with a multiband Fermi surface, where states near the Γ point are dominated by in-plane B-p_x, p_y orbitals, while zone-boundary states are primarily derived from out-of-plane B-p_z orbitals. The electron-phonon coupling is determined to be λ= 0.64 for both materials, driven by the rigid covalent B-B and B-C honeycomb networks. By solving the anisotropic Eliashberg equations, we predict that CaB_4C_2 and MgB_4C_2 are nodeless two-gap superconductors with critical temperatures (T_c) of 33.4 K and 33.8 K, respectively, at a Coulomb pseudopotential of μ= 0.10. Furthermore, the superconducting state remains robust under increased Coulomb repulsion (μ= 0.13), retaining elevated T_c values of 31.2 K and 30.9 K, respectively. These findings establish MB_4C_2 monolayers as promising candidates for nanoscale superconducting applications and enrich the family of two-dimensional multigap superconductors.
ER -