Three-dimensional topological Dirac materials

Rövid cím: 
Three-dimensional topological Dirac materials
2016. 09. 09. 10:15
BME Fizikai Intézet, Elméleti Fizika Tanszék, Budafoki út 8. F-épület, III lépcsőház, szemináriumi szoba
Andreas Schnyder (MPI Stuttgart)

Although topologically nontrivial properties are normally associated with insulating phases, recent developments have shown that (semi)metallic phases can also be topological. In this talk, I will survey recent developments regarding the topological classifications of (semi)metallic materials in terms of crystal symmetries [1,2]. As a concrete examples, I will present results about the recently discovered compound Ca3P2 [3], which has a line of Dirac nodes near the Fermi energy. I will discuss the topological properties of Ca3P2 in terms of a low-energy effective theory and a tight-binding model, derived from ab initio DFT calculations. The microscopic model for Ca3P2 shows that the drumhead surface states have a rather weak dispersion, which implies that correlation effects are enhanced at the surface of Ca3P2. Furthermore, I will discuss the parity anomaly that exists in this nodal-line semimetal and show how it is connected to unusual transport phenomena. If time permits, I will also survey the topological properties of the Dirac materials A3EO [4], where A denotes an alkaline earth metal, while E stands for Pb or Sn. I will discuss the magnetic properties of this Dirac system and show that a strong Zeeman field splits the gapped Dirac cones into ungapped Weyl points, which are protected by a quantized Chern number.


[1] Ching-Kai Chiu, Andreas P. Schnyder, Phys. Rev. B 90, 205136 (2014).
[2] Y. X. Zhao, Andreas P. Schnyder, Z. D. Wang, Phys. Rev. Lett. 116, 156402 (2016).
[3] Y.-H. Chan, Ching-Kai Chiu, M. Y. Chou, A. P. Schnyder, Phys. Rev. B 93, 205132 (2016).
[4] Ching-Kai Chiu, Y.-H. Chan, Xiao Li, Y. Nohara, A. P. Schnyder , arXiv:1606.03456 (submitted).