Strain-driven topological quantum phase transition in (pseudo)cubic (mixed)-Cs/MA/FA halide perovskites

Abstract

The centrosymmetric halide perovskites undergo a continuous phase transition from a trivial to topological insulator at the critical value of strain. Contrarily, in noncentrosymmetric halide perovskites, this phase transition is discontinuous. The noncentrosymmetry does not stabilize the gapless state, causing discontinuity in the bandgap. We have employed density functional theory and Slater–Koster formalism-based tight-binding Hamiltonian studies to understand the evolution of band topology under compressive strain. Our study shows that both cubic and pseudocubic FAPbI₃ undergo a Pb s–p band inversion at γ (V/V₀) = 0.76 and 0.73, respectively. The pseudocubic structure shows two conducting states around, M unlike the cubic counterpart. The Pb–Pb second nearest neighbor interactions determine this topological phase transition. Alongside, we have modeled mixed cation halide perovskites Cs_xMA_1−xPbI₃ (x = 0.25, 0.50 and 0.75) to study their topological properties. In addition, the structural stability of different strained configurations strengthens the experimental relevance.