Surfaces of axion insulators
Surfaces of axion insulators
Axion insulators are magnetic topological insulators in which the nontrivial ${\mathbb{Z}}_{2}$ index is protected by inversion symmetry instead of time-reversal symmetry. The naturally gapped surfaces of axion insulators give rise to a half-quantized surface anomalous Hall conductivity (AHC), but the sign of the surface AHC cannot be determined from topological …