Geunsik Lee, Muhammad A. Farhan, Jun Sung Kim, Ji Hoon Shim
Low energy electronic structures in AMnBi$_2$ (A=alkaline earths) are investigated using a first-principles calculation and a tight-binding method. An anisotropic Dirac dispersion is induced by the checkerboard arrangement of alkaline earth atoms above and below the Bi square net in AMnBi$_2$. SrMnBi$_2$ and CaMnBi$_2$ have different nature of the Dirac dispersion due to different stacking of nearby A layers, where the eclipsed- and staggered-type stacking cause two-fold and four-fold rotational symmetries, respectively. Using the tight binding analysis, we show the chirality of the anisotropic Dirac electrons as well as the sizable spin orbit coupling effect in a Bi square net. We suggest that Bi square net provides a platform for the interplay between anisotropic Dirac electrons and neighboring environment such as magnetism and structural changes.
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http://arxiv.org/abs/1301.1087
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