Valley-Selective Transport through Structural Domain Walls in Rhombohedral Graphene Quarter Metals

Domain walls separating quarter metals with opposite valley polarizations have recently been imaged in rhombohedral graphene multilayers. Depending on their formation mechanism, these walls respond in distinct ways to external magnetic probes. Therefore, understanding their behaviors is critical to the interpretation of experimental results. In this work, we examine domain walls formed from strain-induced one-dimensional structural defects that separate domains with complementary rhombohedral stacking orders. We show that while transport across such domain walls is controlled by the valley degree of freedom, the coupling to a magnetic field is dictated by the momentum-space chirality encoded in the Hamiltonian. As a consequence, structural domain walls are rendered electronically opaque by an applied magnetic field, while intrinsic domain walls formed by spontaneous valley symmetry breaking are unstable in the presence of such an ordering field and can be eliminated. This dichotomy allows the two types of domain walls to be distinguished in a magnetotransport experiment.