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<p>Two-dimensional (2D) topological insulators with symmetry-protected helical edge states have drawn significant interest. The recently synthesized layered 2D electride BaCu features a monolayer structure with intriguing band crossings near Fermi level and a low exfoliation energy. In this study, first-principles calculations combined with symmetry analysis reveal that the BaCu monolayer behaves as a 2D topological insulator (TI) nature. When integrated with a 30° twisted <InlineEquation ID="IEq1"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="41524_2025_1716_Article_IEq1.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="71" /> </InlineMediaObject> <EquationSource Format="TEX">\(\sqrt{3}\times \sqrt{3}\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msqrt> <mrow> <mn>3</mn> </mrow> </msqrt> <mo>×</mo> <msqrt> <mrow> <mn>3</mn> </mrow> </msqrt> </mrow> </math></EquationSource> </InlineEquation> hexagonal boron nitride (h-BN) supercell, the resulting twisted α/β-BaCu/BN heterobilayers exhibit 2D Weyl points and type-III Dirac points, respectively, demonstrating that twist angle can effectively modulate topological properties. Interestingly, ab initio molecular dynamics (AIMD) simulations reveal a spontaneous transition from the metastable β-BaCu/BN to α-BaCu/BN configuration, indicating a low energy barrier and highlighting the potential for property modulation, emphasizing the versatility of twisted structures for tuning topological states. This work establishes a robust platform for exploring twist-angle-induced topological electride states, broadening the scope for future investigations.</p>

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Two-dimensional Weyl and type-III Dirac semimetals in BaCu monolayer and twisted α/β-BaCu/BN systems

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2025年7月8日

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  • Yiwei Liang,
  • Xinyan Lin,
  • Biao Wan,
  • Yujin Jia,
  • Yuting Qian,
  • Dexi Shao,
  • Huiyang Gou

摘要

Two-dimensional (2D) topological insulators with symmetry-protected helical edge states have drawn significant interest. The recently synthesized layered 2D electride BaCu features a monolayer structure with intriguing band crossings near Fermi level and a low exfoliation energy. In this study, first-principles calculations combined with symmetry analysis reveal that the BaCu monolayer behaves as a 2D topological insulator (TI) nature. When integrated with a 30° twisted \(\sqrt{3}\times \sqrt{3}\) 3 × 3 hexagonal boron nitride (h-BN) supercell, the resulting twisted α/β-BaCu/BN heterobilayers exhibit 2D Weyl points and type-III Dirac points, respectively, demonstrating that twist angle can effectively modulate topological properties. Interestingly, ab initio molecular dynamics (AIMD) simulations reveal a spontaneous transition from the metastable β-BaCu/BN to α-BaCu/BN configuration, indicating a low energy barrier and highlighting the potential for property modulation, emphasizing the versatility of twisted structures for tuning topological states. This work establishes a robust platform for exploring twist-angle-induced topological electride states, broadening the scope for future investigations.