Ca3P2 and other topological semimetals with line nodes and drumhead surface states

Article

关键词: DIRAC SEMIMETAL;    INSULATOR;    SUPERCONDUCTIVITY;    DISCOVERY;    MOBILITY;    GRAPHENE;    FERMIONS;    BULK;   

DOI  :  10.1103/PhysRevB.93.205132

来源: SCIE

【 摘 要 】

As opposed to ordinary metals, whose Fermi surfaces are two dimensional, topological (semi) metals can exhibit protected one-dimensional Fermi lines or zero-dimensional Fermi points, which arise due to an intricate interplay between symmetry and topology of the electronic wave functions. Here, we study how reflection symmetry, time-reversal symmetry, SU(2) spin-rotation symmetry, and inversion symmetry lead to the topological protection of line nodes in three-dimensional semimetals. We obtain the crystalline invariants that guarantee the stability of the line nodes in the bulk and show that a quantized Berry phase leads to the appearance of protected surfaces states, which take the shape of a drumhead. By deriving a relation between the crystalline invariants and the Berry phase, we establish a direct connection between the stability of the line nodes and the drumhead surface states. Furthermore, we show that the dispersion minimum of the drumhead state leads to a Van Hove singularity in the surface density of states, which can serve as an experimental fingerprint of the topological surface state. As a representative example of a topological semimetal, we consider Ca3P2, which has a line of Dirac nodes near the Fermi energy. The topological properties of Ca3P2 are discussed in terms of a low-energy effective theory and a tight-binding model, derived from ab initio DFT calculations. Our 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.

【 授权许可】

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