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

We report the topological phase transition (TPT) in compounds of relatively less explored Zintl family RbZn₄X₃(X = P, As) via<i>first-principles</i>calculation. These intermetallic compounds have already been experimentally synthesized in a<i>KCu₄S₃-type</i>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 TPTs in these materials with external applied pressure and epitaxial strain. The dynamical and mechanical stabilities of these compounds are verified through phonon dispersion and Born stability criteria at ambient and TPT pressure/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<i>Zn-s</i>and<i>P/As-p_zorbitals</i>in the bulk band structure of these materials which is further confirmed using the surface density of states and Fermi arc contour in<i>(001)-plane</i>. The ℤ₂topological invariants (<i>ν</i>₀<i>; ν</i>₁<i>ν</i>₂<i>ν</i>₃) 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 (<i>ν</i>₀<i>; ν</i>₁<i>ν</i>₂<i>ν</i>₃) from (<i>0; 000</i>) to (<i>1; 000</i>), at the particular values of pressure and strain, is another signature of the TPT in these materials.