Converting topological insulators into topological metals within the tetradymite family
Converting topological insulators into topological metals within the tetradymite family
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DOI：
10.1103/physrevb.97.165112
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发表时间：
2017-11
影响因子：
3.7
通讯作者：
K. Chen;N. Aryal;J. Dai;D. Graf;S. Zhang;S. Das;P. Fèvre;F. Bertran;R. Yukawa;K. Horiba;H. Kumigashira;E. Frantzeskakis;F. Fortuna;L. Balicas;A. Santander-Syro;E. Manousakis;R. Baumbach
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文献类型：
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作者：
K. Chen;N. Aryal;J. Dai;D. Graf;S. Zhang;S. Das;P. Fèvre;F. Bertran;R. Yukawa;K. Horiba;H. Kumigashira;E. Frantzeskakis;F. Fortuna;L. Balicas;A. Santander-Syro;E. Manousakis;R. Baumbach
我们报告了一系列可剥落辉辉石化合物的电子能带结构和伴随的费米面，其分子式为 $T_2$$Ch_2$$Pn$，通过对著名的拓扑绝缘体二元 Bi$_2$(Se,Te)$_3$ 进行修改，通过用磷元素 ($Pn$) 替换硫属元素 ($Ch$) 并用四价过渡金属 $T$ $=$ Ti 替换 Bi， Zr或Hf。这会导致电子计数不平衡，并导致层状金属的特征是相对较高的载流子迁移率和块状二维费米表面，其形貌通过第一原理计算得到了很好的描述。有趣的是，平板电子结构计算预测了类狄拉克表面态。与 Bi$_2$Se$_3$ 不同，表面狄拉克能带位于 $\Gamma-$ 点，对于 (Zr,Hf)$_2$Te$_2$(P,As)，在 $\bar {\Gamma}$- 和 $\bar {M}$-点周围分别存在具有强拓扑特征的狄拉克锥，这些点分别高于和低于费米能量。对于 Ti$_2$Te$_2$P，表面状态预计仅存在于 $\bar {M}$ 点周围。与这些预测一致，通过角分辨光电子能谱测量观察到位于费米能量以下的表面态，表明它们与块体金属态共存。因此，这一族材料为开发利用体态和表面态（例如拓扑超导性）的新现象奠定了基础。
We report the electronic band structures and concomitant Fermi surfaces for a family of exfoliable tetradymite compounds with the formula $T_2$$Ch_2$$Pn$, obtained as a modification to the well-known topological insulator binaries Bi$_2$(Se,Te)$_3$ by replacing one chalcogen ($Ch$) with a pnictogen ($Pn$) and Bi with the tetravalent transition metals $T$ $=$ Ti, Zr, or Hf. This imbalances the electron count and results in layered metals characterized by relatively high carrier mobilities and bulk two-dimensional Fermi surfaces whose topography is well-described by first principles calculations. Intriguingly, slab electronic structure calculations predict Dirac-like surface states. In contrast to Bi$_2$Se$_3$, where the surface Dirac bands are at the $\Gamma-$point, for (Zr,Hf)$_2$Te$_2$(P,As) there are Dirac cones of strong topological character around both the $\bar {\Gamma}$- and $\bar {M}$-points which are above and below the Fermi energy, respectively. For Ti$_2$Te$_2$P the surface state is predicted to exist only around the $\bar {M}$-point. In agreement with these predictions, the surface states that are located below the Fermi energy are observed by angle resolved photoemission spectroscopy measurements, revealing that they coexist with the bulk metallic state. Thus, this family of materials provides a foundation upon which to develop novel phenomena that exploit both the bulk and surface states (e.g., topological superconductivity).