Prediction of superconductivity in bilayer borophenes

• Published in: RSC advances Vol. 11; no. 63; pp. 422 - 4227
• Main Authors: Yan, Luo, Ku, Ruiqi, Zou, Jing, Zhou, Liujiang, Zhao, Jijun, Jiang, Xue, Wang, Bao-Tian
• Format: Journal Article
• Language: English
• Published: England Royal Society of Chemistry 17.12.2021; The Royal Society of Chemistry
• Subjects: BCS theory; Bilayers; Borophene; Chemistry; Copper; Density functional theory; Monolayers; Phonons; Silver; Structural stability; Substrates; Superconductivity; Two dimensional materials
• ISSN: 2046-2069; 2046-2069
• DOI: 10.1039/d1ra08014h

Borophenes and related two-dimensional materials have exhibited many exotic properties, especially for superconductivity, although the superconductivity of single-layer borophene is suppressed by the strains or doping from its substrates. Intriguingly, bilayer (BL) borophenes can be stabilized by appropriate pillar density and hexagonal holes density, rather than being supported by Ag(111) or Cu(111) substrates. Thus, we studied the two most stable structures, namely BL-B8 and BL-B30, stabilized by the above-mentioned two methods. Within density functional theory and Bardeen-Cooper-Schrieffer theory framework, their stability, electron structures, and phonon properties, as well as possible superconductivity are systematically scrutinized. The metallic BL-B8 and BL-B30 exhibit intrinsic superconducting features with superconductivity transition temperatures ( T c ) of 11.9 and 4.9 K, respectively. The low frequency (below 400 cm −1 ) consisting of out-of-plane vibrations of boron atoms plays crucial rule in their superconductivity. In particular, a Kohn anomaly appears at the Γ point in BL-B8, leading to substantial electron-phonon coupling. Here, our findings will provide instructive clues for experimentally determining the superconductivity of borophene and will broaden the two-dimensional superconductor family. Bilayer borophene B8 and B30 are BCS-superconductors with T c of 11.9 and 4.9 K, respectively.