Prediction of superconductivity and charge density wave in monolayer h−BN via functionalization with Si-N layer

Abstract

Inspired by the successful synthesis of two-dimensional (2D) MoSi2N4 and WSi2N4 [Y. L. Hong et al., Science 369, 670 (2020)], which demonstrates that Si-N layers can act as effective modification layers on 2D materials, we investigate superconductivity and charge density waves (CDWs) of hexagonal boron nitride (h−BN) passivated with a Si-N layer based on first-principles calculations. Our results demonstrate that h-BN undergoes a transition from an insulator to a phonon-mediated superconductor with the transition temperature (Tc) of 14.3 K when it is functionalized with a Si-N layer on one side. The electron-phonon coupling (EPC) of BN2Si is primarily attributed to the coupling between electrons in N-pz orbitals and the low-frequency in-plane vibrational modes of Si and N atoms, as well as higher-frequency out-of-plane vibration modes of N and B atoms. By applying 5% biaxial tensile strain, the EPC constant λ increases from 0.66 to 1.82, resulting in a significantly enhanced Tc of 34.9 K. However, when the biaxial tensile strain reaches 6%, an obvious soft mode emerges in the lowest acoustic branch of phonon curves, indicating the presence of a CDW. The origin of the instabilities is analyzed based on Lindhard electron susceptibility and the phonon linewidths, revealing that the CDW is driven by both Fermi-surface nesting and EPC. Thus, the predicted BN2Si presents a promising platform for exploring 2D superconductivity and CDWs.

Source-reported materials — not catalogue approval

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