Ferroelectric heterobilayer with tunable first- and higher-order topological states

As conceptual milestones of nontrivial phenomenon, Z2 topological insulators (TIs) and higher-order TIs (HOTIs) have greatly reshaped the landscape of fundamental physics and materials. However, despite the exciting progress, a tunable topological phase transition between Z2 TIs and HOTIs remains elusive. Here, using a tight-binding model and first-principles calculations, we propose that ferroelectric switching can be a straightforward and efficient way for engineering the Z2 TIs and HOTIs phases with strikingly different bulk-boundary correspondence. Remarkably, based on the Wannier charge centers, edge states, and corner states analysis, we identify the ferroelectric heterobilayer composed of MgAl2Se4 and In2S3 as a material candidate of the predicted topological phase transition. Obviously, the ferroelectric switching opens up a technological avenue to bridge the first-and higher-order topologies with high possibility of innovative applications in topotronic and ferroelectric devices.