Categoria

Seminario

Data

10 Aprile 2017 15:30 - 16:30

Luogo

14 - 15 IV piano St. 9

Affiliation

University of Nagoya (Japan)

In the presence of spin-orbital coupling, the node structures are determined by the group theory where the symmetry operation in a crystal lattice is followed by spin. Such a node is stabilized by crystal symmetry. Above all, in odd-parity SCs, Blount generally proved that a line node is unstable under the mirror-reflection symmetry, which is known as the Blount?s theorem. Also, as the counterexample of his statement, Micklitz and Norman indicated that there exists a stable line node in nonsymmorphic SCs in which the combination of inversion symmetry and twofold screw symmetry exists. We are interested in the connection between the group theoretical results and the topological classification. To show this, we calculate topological numbers of nodes under the mirror-reflection symmetry. As a result, we found that the topological classification not only includes the Blount?s theorem but also updates the instability of line node via the bulk-boundary correspondence. Furthermore, taking into account the nonperiodic boundary condition on a tight-binding Hamiltonian, we extend the topological node stability to the case of nonsymmorphic SCs. In conclusion, the stable line node suggested by Micklitz and Norman is also a topological object. References: SK, et al., PRB, 90, 024516 (2014); SK et al., PRB 94, 134512 (2016).

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