Scattering of Magnons at Graphene Quantum-Hall-Magnet Junctions

Motivated by recent nonlocal transport studies of quantum-Hall-magnet (QHM) states formed in monolayer graphene's N = 0 Landau level, we study the scattering of QHM magnons by gate-controlled junctions between states with different integer filling factors nu. For the nu = 1 vertical bar-1 vertical bar 1 geometry we find that 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 vertical bar 0 vertical bar 1 geometry, we find that kinematic constraints completely block magnon transmission if the incident angle exceeds a critical value. Our results explain the suppressed nonlocal-voltage signals observed in the nu = 1 vertical bar 0 vertical bar 1 case. We use our theory to propose that valley waves generated at nu = -1 vertical bar 1 junctions and magnons can be used in combination to probe the spin or valley flavor structure of QHM states at integer and fractional filling factors.

Automated summary

Research shows that there are certain patterns in the scattering of magnons between states with different filling factors, with chiral scattering occurring when the junction lacks mirror symmetry; kinematic constraints can completely block magnon transmission, explaining the suppression of certain voltage signals observed; the combination of valley waves and magnons can be used to probe the spin or valley flavor structure of QHM states at integer and fractional filling factors.