Quantum Orbital-to-Spin Conversion by Ferroelectric Topological Switch

Recent advances in manipulating orbital degrees of freedom in electronic systems have sparked interest in the novel field of orbitronics, emphasizing the need to integrate it with existing spintronic paradigms in next-generation devices. Here, we outline the principle of quantum orbital-to-spin conversion, a mechanism that converts the quantized orbital Hall effect into the quantum spin Hall effect by ferroelectricity. We show that, by switching electric polarization, the system can be driven through a topological phase transition between the second-order and conventional topological insulator states, triggering a process that transforms the spin-dependent anomalous Hall effect into the orbital Hall effect. Depending on the electronic structure, this allows radical change of the nature of quantized Hall transport of angular momentum from purely orbital-dominated to solely spin-dominated. Our work uncovers the unexplored aspects of spin-orbital interplay, which allow for natural fusion of spintronics, orbitronics, and topological electronics within a single device.