Data for: Hidden non-collinear spin-order induced topological surface states

Rare-earth monopnictides are a family of materials simultaneously
displaying complex magnetism, strong electronic correlation, and
topological band structure. The recently discovered emergent arc-like
surface states in these materials have been attributed to the
multi-wave-vector antiferromagnetic order, yet the direct experimental
evidence has been elusive. Here we report the observation of non-collinear
antiferromagnetic order with multiple modulations using spin-polarized
scanning tunneling microscopy. Moreover, we discover a hidden
spin-rotation transition of single-to-multiple modulations 2 K below the
Neel temperature. The hidden transition coincides with the onset of the
surface state splitting observed by our angle-resolved photoemission
spectroscopy measurements. Single modulation gives rise to a band
inversion with induced topological surface states in a local momentum
region while the full Brillouin zone carries trivial topological indices,
and multiple modulation further splits the surface bands via non-collinear
spin tilting, as revealed by our calculations. The direct evidence of the
non-collinear spin order in NdSb not only clarifies the mechanism of the
emergent topological surface states but also opens up a new paradigm of
control and manipulation of band topology with magnetism.