Universitą degli studi di Modena e Reggio Emilia

Controlling topology through ferroelectricity

Topological insulators are a special class of materials with properties that are robust against possible perturbations and disorder, making them “non-trivial”. In their bulk they are indeed insulating, but at their boundaries and surfaces current can flow almost without dissipation. In order to make them useful for technological applications, it is important to be able to switch on and off their topological properties, and correspondingly their metallic boundary states. Up to now, most approaches have relied on volatile effects, where the transformation from a topological to a so-called “trivial” state requires energy to be maintained.
Marco Gibertini from FIM together with Antimo Marrazzo from UniTs now predict, through a combination of analytical models and first-principles simulations, that it is possible to exploit ferroelectricity to control topology in a non-volatile way. By combining two “trivial” two-dimensional materials, one being ferroelectric, it is possible to create a heterostructure where in one ferroelectric polarization state the system is topological (already intriguing given the non topological nature of the parent materials), while in the opposite polarization state it is trivial, so that an external electric field not only controls the polarization direction but also the topological state. The study is now published on npj 2D Materials and Applications, and will stimulate experimental groups to validate this prediction.