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Abstract:
Recently the presence of topologically protected edge-states in
Bi14Rh3I9 was confirmed by scanning tunnelling microscopy consolidating
this compound as a weak 3D topological insulator (TI). Here, we present
a density-functional-theory-based study on a family of TIs derived from
the Bi14Rh3I9 parent structure via substitution of Ru, Pd, Os, Ir and Pt
for Rh. Comparative analysis of the band-structures throughout the
entire series is done by means of a unified minimalistic tight-binding
model that evinces strong similarity between the quantum-spin-Hall (QSH)
layer in Bi14Rh3I9 and graphene in terms of p(z) -molecular orbitals.
Topologically non-trivial energy gaps are found for the Ir-, Rh-, Pt-and
Pd-based systems, whereas the Os-and Ru-systems remain trivial.
Furthermore, the energy position of the metal d-band centre is
identified as the parameter which governs the evolution of the
topological character of the band structure through the whole family of
TIs. The d-band position is shown to correlate with the chemical bonding
within the QSH layers, thus revealing how the chemical nature of the
constituents affects the topological band character.
