Magnetic ordering and topology in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>Mn</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:msub><mml:mi>Bi</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:msub><mml:mi>Te</mml:mi><mml:mn>5</mml:mn></mml:msub></mml:mrow></mml:math> and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>Mn</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:msub><mml:mi>Sb</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:msub><mml:mi>Te</mml:mi><mml:mn>5</mml:mn></mml:msub></mml:mrow></mml:math> van der Waals materials
С. В. Еремеев, M. M. Otrokov, A. Ernst, Е. В. Чулков
Abstract
Using density functional theory calculations we study atomic, electronic, and magnetic structures and their influence on the topological phase of ${\mathrm{Mn}}_{2}{\mathrm{Bi}}_{2}{\mathrm{Te}}_{5}$ and ${\mathrm{Mn}}_{2}{\mathrm{Sb}}_{2}{\mathrm{Te}}_{5}$ van der Waals compounds. Our results show that the antiferromagnetic topological insulator (AFM TI) phase in ${\mathrm{Mn}}_{2}{\mathrm{Bi}}_{2}{\mathrm{Te}}_{5}$ is robust both to details of the magnetic ordering within its structural units, nonuple layer (NL) blocks, and the type of atomic layer stacking, NaCl-type ABC or NiAs-type ABAC, within the (${\mathrm{MnTe})}_{2}$ sublattice. The structure with the NiAs-type stacking is energetically more favorable for both compounds. However, for ${\mathrm{Mn}}_{2}{\mathrm{Sb}}_{2}{\mathrm{Te}}_{5}$ the AFM TI phase is realized in the unstable structure with ABC stacking while it is a Dirac semimetal in favorable structure with NiAs stacking within a (${\mathrm{MnTe})}_{2}$ sublattice. We also show that imposing the overall ferromagnetic state by applying an external magnetic field can drive the ${\mathrm{Mn}}_{2}\mathrm{Bi}{(\mathrm{Sb})}_{2}{\mathrm{Te}}_{5}$ compounds into different topologically nontrivial phases like axion insulator or Weyl semimetal.