55 research outputs found
Hall effect of ferro/antiferromagnetic wallpaper fermions
Nonsymmorphic crystals can host characteristic double surface Dirac cones
with fourfold degeneracy on the Dirac points, called wallpaper fermion,
protected by wallpaper group symmetry. We clarify the charge and spin Hall
effect of wallpaper fermions in the presence of the (anti)ferromagnetism.Based
on a four-sublattice model, we construct the effective Hamiltonian of wallpaper
fermions coupled with the ferromagnetic or antiferromagnetic moment.Both
ferromagnetic and antiferromagnetic moments induce an energy gap for the
wallpaper fermions, leading to quantized (spin) Hall conductivity. The
ferromagnetic wallpaper fermion induces the Hall conductivity quantized into
, which is twice that for a single Dirac fermion on the surface of
topological insulators. On the other hand, the spin Hall conductivity decays
and reaches to be a finite value as the antiferromagnetic coupling increases.
We also show that the results above are valid for a general model of wallpaper
fermions from symmetry consideration.Comment: 9 pages, 22 figure
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