自旋轨道耦合变号驱动的氮化铊中拓扑绝缘体到Dirac半金属跃迁
Topological Insulator to Dirac Semimetal Transition Driven by Sign Change of Spin-Orbit Coupling in Thallium Nitride
摘要：
基于第一性原理计算，我们发现TlN是一种具有有效负自旋轨道耦合$λ_{eff} < 0$的三维拓扑绝缘体，其表面态具有相反的自旋动量锁定效应. $λ_{eff}$的符号取决于N- $2p$和Tl- $5d$态之间的杂化，并且可以通过晶格应变或化学取代从负到正进行调谐，从而驱动系统成为在其体态具有3D狄拉克锥的狄拉克半金属。这种拓扑相变可以在不破坏任何晶体对称性的情况下通过电子机制实现。
英文摘要：
Based on the first-principles calculations, we reveal that TlN, a simple binary compound with Wurtzite structure, is a three-dimensional (3D) topological insulator (TI) with effectively negative spin-orbit coupling $λ_{eff} < 0$, which makes it distinguished from other TIs by showing opposite spin-momentum locking effect in its surface states. The sign of $λ_{eff}$ depends on the hybridization between N-$2p$ and Tl-$5d$ states, and can be tuned from negative to postive by lattice strain or chemical substitution, which drive the system into a Dirac semimetal with 3D Dirac cones in its bulk states. Such topological phase transition can be realized by electronic mechanism without breaking any crystal symmetry.
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