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Abstract:
One important feature of surface states in topological insulators is the
so-called "spin-momentum locking," which means that electron spin is
oriented along a fixed direction for a given momentum and forms a
texture in the momentum space. In this work, we study spin textures of
two typical topological insulators in Hg-based chalcogenides, namely,
HgTe and HgS, based on both the first-principles calculation and the
eight-band Kane model. We find opposite helicities of spin textures
between these two materials, originating from the opposite signs of
spin-orbit couplings. Based on the effective Kane model, we present a
physical picture to understand opposite spin textures in these two
materials with the help of the relationship between spin textures and
mirror Chern numbers. We also reveal the existence of gapless states at
the interface between HgTe and HgS due to the opposite spin textures and
opposite mirror Chern numbers.