CdGeSb $_2$和CdSnSb $_2$中的压力诱导拓扑相变
Pressure-Induced Topological Phase Transitions in CdGeSb$_2$ and CdSnSb$_2$
摘要：
由外界微扰引起的材料拓扑量子相变（TQPT）通常以布里渊区中的带接触点为特征。简并带接触点附近的低能激发在保持表面态的拓扑保护的同时容纳不同类型的费米子。不同的可调拓扑相位的相互作用提供了一个洞察的拓扑字符的演变。本文利用第一性原理计算研究了CdGeSb $_2$和CdSnSb $_2$黄铜矿中TQPT的存在与流体静压的关系。在环境压力下，这两种材料都是具有有限带隙的拓扑绝缘体，其在$Γ$点处的价带轨道顺序为$s$和$p_x$、$p_y$。在静水压力的应用的带隙减小，并在相变的临界点，这些材料变成狄拉克半金属。在进一步增加的压力超过临界点，带反转恢复，使他们平凡的绝缘体。压力引起的变化，从非平凡到平凡的相位带拓扑结构也被捕获的Lüttinger模型哈密顿计算。我们的模型表明，在驱动相变的前沿带中的压力引起的各向异性所发挥的关键作用。这些发现为实验实现TQPT提供了一个现实的和有前途的平台。
英文摘要：
Topological quantum phase transitions (TQPTs) in a material induced by external perturbations are often characterized by band touching points in the Brillouin zone. The low-energy excitations near the degenerate band touching points host different types of fermions while preserving the topological protection of surface states. An interplay of different tunable topological phases offers an insight into the evolution of the topological character. In this paper, we study the occurrence of TQPTs as a function of hydrostatic pressure in CdGeSb$_2$ and CdSnSb$_2$ chalcopyrites, using the first-principles calculations. At ambient pressure, both materials are topological insulators having a finite band gap with inverted order of Sb-$s$ and Sb-$p_x$,$p_y$ orbitals of valence bands at the $Γ$ point. On the application of hydrostatic pressure the band gap reduces, and at the critical point of the phase transition, these materials turn into Dirac semimetals. On further increasing the pressure beyond the critical point, the band inversion is reverted making them trivial insulators. The pressure-induced change in band topology from non-trivial to trivial phase is also captured by Lüttinger model Hamiltonian calculations. Our model demonstrates the critical role played by a pressure-induced anisotropy in frontier bands in driving the phase transitions. These theoretical findings of peculiar coexistence of multiple topological phases in the same material provide a realistic and promising platform for the experimental realization of the TQPT.
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