Unraveling the topological phase in Zintl semiconductors RbZn4X3 (X=P, As) through band engineering.

Abstract

We report the topological phase transition in compounds of relatively less explored Zintl family RbZn4X3 (X=P, As) via first-principles calculation. These intermetallic compounds have already been experimentally synthesized in a KCu4S3-type tetragonal structure (P4/mmm) and reported to have a topologically trivial semimetallic nature with a direct band gap. We thoroughly studied the electronic structure, stability of RbZn4X3 (X=P, As) and demonstrated the topological phase transitions in these materials with external applied pressure and epitaxial strain. The dynamical stability of these compounds is verified through phonon dispersion at all values of topological phase transition pressure and strain. A topologically non-trivial phase in RbZn4P3 (RbZn4As3) is observed at 45 GPa (38 GPa) of hydrostatic pressure and 10% (8%) of epitaxial strain. This non-trivial phase is identified by band inversion between Zn-s and P/As-pzorbitals in the bulk band structure of these materials which is further confirmed using the surface density of states and Fermi arc contour in (001)-plane. The ℤ2 topological invariants (ν0; ν1ν2ν3) for these materials are calculated using the product of parities of all filled bands (Kane and Mele model) and the evolution of Wannier charge centers (Wilson loop method). The change in values of (ν0; ν1ν2ν3) from (0;000) to (1,000), at the particular values of pressure and strain, is another signature of the topological phase transition in these materials. .