Ferroelectric Control of Layer-Resolved Spin and Orbital Transport in a Topological Heterobilayer.

Ferroelectric switching in van der Waals heterostructures provides a powerful route to reconfiguring quantum states and their associated transport responses. Here, we propose a ferroelectric topological heterobilayer in which the stepwise reversal of polarization in the two monolayers enables selective control of spin and orbital transport with reduced mutual interference. Using first-principles calculations, we identify the In2Te3/In2Se3 heterobilayer as a candidate, where this stepwise polarization switching drives successive topological phase transitions from second-order topological to quantum spin Hall insulators and eventually to a trivial metal. These three phases exhibit distinct transport characteristics, including pure orbital Hall effect (OHE), layer-resolved coexistence of spin Hall effect (SHE) and OHE, and a metallic state with simultaneously enhanced SHE and OHE, accompanied by pronounced changes in the layer distribution of carriers. Our work highlights ferroelectric topological heterobilayers as a promising platform for controlling and characterizing spin-orbitronic transport, with potential for integrated spintronic and orbitronic devices.