Scattering of magnons at graphene quantum-Hall-magnet junctions*

Motivated by recent non-local transport studies of quantum-Hall-magnet (QHM) states formed in monolayer graphene’s N = 0 Landau level (Wei et.al Science 362, 229-233; Zhou et.al Nature Physics 16, 154–158(2020)), we study the scattering of QHM magnons by gate-controlled junctions between states with different integer filling factors \nu. For the \nu = 1| − 1|1 geometry we find magnons are weakly scattered by electric potential variation in the junction region, and that the scattering is chiral when the junction lacks a mirror symmetry. For the \nu = 1|0|1 geometry, we find that kinematic constraints completely block magnon transmission if the incident angle exceeds a critical value. Our results explain the suppressed non-local-voltage signals observed in the \nu = 1|0|1 case.