Anisotropic Dirac electronic structures of AMnBi$_2$ (A=Sr, Ca)

TL;DR

This study investigates the anisotropic Dirac electronic structures in AMnBi2 compounds using first-principles and tight-binding calculations, revealing unique dispersion, chirality, and spin-orbit effects influenced by atomic stacking.

Contribution

It introduces a detailed analysis of anisotropic Dirac dispersions in AMnBi2, highlighting the effects of atomic stacking and spin-orbit coupling on electronic properties.

Findings

Anisotropic Dirac dispersion is induced by A atom arrangements.

Different stacking of A layers leads to distinct Dirac dispersions.

Sizable spin-orbit coupling affects the Dirac electrons.

Abstract

Low energy electronic structures in AMnBi2 (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 A atoms above and below the Bi square net in AMnBi2. SrMnBi2 and CaMnBi2 have a different kind of Dirac dispersion due to the different stacking of nearby A layers, where each Sr (Ca) of one side appears at the overlapped (alternate) position of the same element at the other side. Using the tight binding analysis, we reveal the chirality of the anisotropic Dirac electrons as well as the sizable spin-orbit coupling effect in the Bi square net. We suggest that the Bi square net provides a platform for the interplay between anisotropic Dirac electrons and the neighboring environment such as magnetism and structural changes.