Stacking-Induced Topological Phase Transitions in Designer Bilayer Heterostructures

Topological materials are poised to transform spintronic and quantum technologies; however, discovering systems with both robust and tunable topological phases remain a major challenge. In this work, we propose a materials-design strategy to engineer novel two-dimensional topologically nontrivial phases by strategically stacking otherwise trivial Rashba monolayers¹. Using BiSb as a representative system, we demonstrate that an inverted stacking of two BiSb monolayers (forming a BiSb–SbBi bilayer) induces a topologically nontrivial phase, despite each isolated monolayer being trivial. This emergent nontrivial topology originates from a subtle interplay between spin-orbit coupling (SOC) and interlayer electronic tunneling. The topological character of this system is tuned by an external electric field, enabling gate-controlled topological switching. Moreover, introducing a twist between the layers generates a moiré potential that hosts topologically nontrivial solitons separated by trivial domains within the same moiré supercell. These findings unveil a versatile pathway for engineering tunable topological phases through stacking and twisting in layered materials.

 

1. Bordoloi et al., "Tunable stacking-driven topological phase transitions in pnictide layers," arXiv:2504.21126 (2025).