Probing emerging two-dimensional (2D) superconductors, including 2D metal borocarbides, has recently garnered significant research interest. However, 2D superconducting Ti-B-C monolayers with unique boron motifs have yet to be discovered. In this study, we conducted a comprehensive investigation of the 2D Ti-B-C system through a first-principles structure search method and identified two stable metallic monolayers, TiB₃C and Ti₂B₃C₂, featuring unanticipated kagome boron layers. Electron–phonon coupling (EPC) simulations reveal that both monolayers exhibit phonon-mediated superconductivity, with superconducting transition temperatures (T_c) of 3.2 and 6.5 K, respectively. Furthermore, biaxial compressive strain enhances superconductivity in TiB₃C, increasing its T_c to 11.3 K under −2 % strain, while biaxial tensile train elevates the T_c of Ti₂B₃C₂ to 15.5 K under 7 % strain. This improvement in superconductivity is primarily attributed to the increase in EPC strength. Additionally, we designed a novel TiB₃CH₂ monolayer with metallic characteristics using a hydrogenation strategy. This monolayer exhibits a significantly higher T_c of 18.7 K, chiefly due to strong coupling between Ti 3d electron states near the Fermi level and mid-frequency B-, C-, and H-associated phonons. Our findings provide valuable insights into 2D boron–carbon-based superconductors containing metals and pave the way for designing new 2D superconducting materials.

中文翻译：

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新兴的二维超导体 TiB3C 和 Ti2B3C2 与单层笼目硼吩


探测新兴的二维 （2D） 超导体，包括 2D 金属碳化硼，最近引起了研究的极大兴趣。然而，具有独特硼基序的 2D 超导 Ti-B-C 单层尚未被发现。在这项研究中，我们通过第一性原理结构搜索方法对 2D Ti-B-C 系统进行了全面研究，并确定了两个稳定的金属单层 TiB ₃ C 和 Ti ₂ B ₃ C ₂ ，具有意想不到的笼目硼层。电子-声子耦合 （EPC） 模拟表明，两种单分子层都表现出声子介导的超导性，超导转变温度 （T _c ） 分别为 3.2 和 6.5 K。此外，双轴压缩应变增强了 TiB ₃ C 的超导性，在 -2 % 应变下将其 T _c 增加到 11.3 K，而双轴拉伸序列在 7 % 应变下将 Ti ₂ B ₃ C ₂ 的 T _c 升高到 15.5 K。超导性的这种改进主要归因于 EPC 强度的增加。此外，我们使用氢化策略设计了一种具有金属特性的新型 TiB ₃ CH ₂ 单层。该单分子层表现出明显更高的 T _c 值，为 18.7 K，主要是由于费米能级附近的 Ti 3d 电子态与中频 B-、C 和 H 相关声子之间的强耦合。我们的研究结果为含金属的 2D 硼碳基超导体提供了有价值的见解，并为设计新的 2D 超导材料铺平了道路。