Multicomponent Magnetic Domain Walls in Rhombohedral Graphene

Abstract

Spatial textures of magnetic order, such as domain walls and skyrmions, are fundamental objects in magnetism. In rhombohedral multilayer graphene, magnetic order involves spin and valley degrees of freedom, opening the possibility of qualitatively new spatial textures. Here, we explore this possibility through a microscopic study of a one-dimensional domain wall in the valley-imbalanced quarter-metal phase of rhombohedral graphene. We uncover two different classes of domain walls. One resembles a conventional magnetic domain wall, locally rotating between the two bulk states, whereas the other is intrinsically multicomponent and explores states that are not occupied in either bulk domain. Which texture is realized is controlled by the competition between intervalley Hund's coupling and spin-orbit coupling, and we identify experimental signatures to distinguish them. We further show that, in a superconducting junction formed across the wall, the superconducting phase difference couples directly to the intervalley-coherent phase of the texture. Precession of this internal phase can therefore generate a voltage across the junction. Our theory shows that rhombohedral graphene indeed has magnetic textures beyond conventional magnet and that their dynamics can couple to superconducting transport.