paper

Rotation Anomaly and Topological Crystalline Insulators

arXiv:1709.01929 · doi:10.1126/sciadv.aat2374

Abstract

We show that in the presence of -fold rotation symmetries and time-reversal symmetry, the number of fermion flavors must be a multiple of () on two-dimensional lattices, a stronger version of the well-known fermion doubling theorem in the presence of only time-reversal symmetry. The violation of the multiplication theorems indicates anomalies, and may only occur on the surface of new classes of topological crystalline insulators. Put on a cylinder, these states have Dirac cones on the top and on the bottom surfaces, connected by helical edge modes on the side surface.

4+6 pages, 3+2 figures and 1 table

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