Coexistence of quantum spin Hall and magnetic states in zigzag bismuth nanoribbons

Using first-principles calculations, we demonstrate the realization of an unusual state in a bismuth nanoribbon passivated with nitrogen atoms along one of the edges. In this novel phase, the quantum spin Hall state on one edge of the nanoribbon coexists with the ferromagnetism on the other edge [1]. We find that this coexistence of states is robust and that it is exhibited even when the nitrogen-decorated nanoribbon is placed on a substrate. In addition, using an undecorated bismuth nanoribbon on hexagonal boron nitride as a proof-of-principle heterostructure, we show that the combination of non-trivial topology and magnetism can potentially exist even without passivation with nitrogen-atoms. This work demonstrates how chemical modifications and/or simple vertical stacking of van der Waals layered crystals can be used as a materials design approach for creating novel phases of matter.

[1] Ivan I. Naumov and Pratibha Dev, Appl. Phys. Lett. 123, 093104 (2023).