检验二维圆锥模型描述三维ZrTe5的有效性
Examining the validity of the two-dimensional conical model to describe the three-dimensional ZrTe5
摘要：
理解三维层状化合物ZrTe 5的低能激发态仍然是新型拓扑材料研究中的一个挑战性问题。最近，提出了一种二维圆锥模型来解释3D ZrTe 5中的实验光谱学，Martino等人[Phys. Rev. Lett. 122，217402（2019）]。受此工作的启发，本文对该模型在无外磁场和有外磁场两种情况下的光学电导率进行了系统的理论研究，进一步证明了该模型的有效性，并发现在该二维圆锥模型中，由于低能激发的各向异性，在不同方向上的光学电导率存在着完全不同的特性。特别地，对于带间光学电导率，我们发现了Re（σ_x）\sim ω^{1/2}和Re（σ_z）\sim ω^{3/2}对光学频率的渐近依赖关系，它们在带隙绝缘体相和Weyl半金属相都是普适的。磁光电导率Re（σ^ B_{x/z}）在带隙绝缘体相和Weyl半金属相表现出明显的特征，有助于区分这两种相。我们的研究结果将在未来的实验中得到验证，可以为理解ZrTe 5的拓扑性质提供更多的见解。
英文摘要：
Understanding the low-energy excitation state in three-dimensional layered compound ZrTe5 remains a challenging problem in the study of novel topological materials. Recently, a two-dimensional conical model was proposed to explain the experimental optical spectroscopy in the 3D ZrTe5, Martino et al. [Phys. Rev. Lett. 122, 217402 (2019)]. Motivated by this work, in this paper, we perform a systematic theoretical study on the optical conductivity of this model in both cases without and with an external magnetic field to further demonstrate the validity of this model and to recover new physics.We find that there exist completely different characteristics for optical conductivity along different directions, due to anisotropic low-energy excitations in this two-dimensional conical model. Specifically, for the interband optical conductivity, we find asymptotic dependence on the optical frequency as Re(σ_x)\simω^{1/2} and Re(σ_z)\simω^{3/2}, which are universal both in the gapped insulator phase and Weyl semimetal phase. For the magneto-optical conductivity, on the contrary, Re(σ^B_{x/z}) shows distinct signatures in the gapped insulator phase and Weyl semimetal phase, which can help distinguish the two phases. Our results, to be verified in future experiments, could provide more insights into the understanding of the topological nature of ZrTe5.
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