Theory of Magnetic Topology in Rare-Earth Monopnictides

Recent photoemission experiments on rare-earth monopnictide (REPn) magnets have revealed an unusual surface-state splitting, distinct from conventional Zeeman and Rashba effects, in surface bands that exhibit extended degeneracies atypical of standard topological phases. We show that these splittings arise from spontaneously breaking an exact chiral symmetry of a cubic Dirac semimetal parent phase. Using symmetry analysis, we construct a tight-binding model for the relevant Shubnikov group, and examine the topological phase diagram, spectral functions, polarization, and magnetization dependencies. Our results demonstrate that chiral symmetries provide a unified framework for a broad range of experimental observations in REPn materials. We further present experimentally testable predictions and outline opportunities to exploit chiral symmetry-protected surface states. These findings position chiral lattice symmetry as a new quantum resource for engineering tunable surface phenomena in spin-orbit-coupled cubic materials.