Exotic quantum spin Hall effect and anisotropic spin splitting in carbon based TMC₆ (TM = Mo, W) kagome monolayers

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• 作者：Xinru Li^a ; Ying Dai^a ; ^{daiy60@sina.com" class="auth_mail" title="E-mail the corresponding author} ; Yandong Ma^b ; Qilong Sun^a ; Wei Wei^a ; Baibiao Huang^a
• 刊名：Carbon
• 出版年：2016
• 出版时间：November 2016
• 年：2016
• 卷：109
• 期：Complete
• 页码：788-794
• 全文大小：1748 K

文摘

Two dimensional topological insulators with high feasibility and room-temperature band gaps are desirable at present. Here, kagome monolayers TMC₆ (TM = Mo, W) are systematically investigated by density functional theory and molecular dynamics simulations. TMC₆ lattice with one TM layer sandwiched between two trigonal carbon layers is proved to be stable. We identify that band inversion occurs in TMC₆ with opened gaps up to 226 meV, making the system suitable for room temperature applications. By analyzing orbital resolved band structures and partial charge densities, we determine that the band inversion is mainly contributed by TM-d orbitals after introducing spin orbit coupling. The nontrivial topological feature is confirmed by direct calculation of Z₂ invariant (Z₂ = 1) indicating that TMC₆ is quantum spin Hall (QSH) insulator. Distinct from previous QSH insulators, there is spin splitting along Γ→K direction (perpendicular to the mirror plane), while there is no splitting along Γ→M direction (parallel to the mirror plane). Further investigation unravels that the anisotropic spin splitting could be attributed to the in-plane structural inversion asymmetry. TMC₆ kagome monolayers with nontrivial topology and anisotropic spin splitting could open up a way for new generation spintronic and electronic devices.