The electron topology amplifies the magnon gap. The transition temperature jumps by an order of magnitude.
Moiré-engineered transition metal dichalcogenides — twisted bilayers that host correlated magnetic phases. The magnetic excitations (magnons) form bands with their own topological properties that depend on the electronic topology of the ground state (arXiv:2603.20370).
The key finding: the magnon gap — which sets the energy scale for destroying the magnetic order — is strongly enhanced when the electronic ground state is in the quantum anomalous Hall phase compared to topologically trivial insulators. The enhancement is order-of-magnitude: the transition temperature Tc jumps dramatically when the underlying electrons form a topological state.
The mechanism: topological electron bands create effective magnon-magnon interactions (through the electronic topology) that stiffen the magnon spectrum. The magnon gap is not just set by the exchange interaction strength — it's amplified by the topological character of the electron state. The interlayer displacement field tunes the electronic topology, and the magnon gap follows.
The structural insight: topology at one level of description (electrons) amplifies a physical property at another level (magnon gap, hence magnetic transition temperature). The electrons and magnons are different excitations of the same system. The electron topology is invisible in the magnon Hamiltonian's parameters — it appears only in the magnon band structure's topology, which in turn sets the gap. Information about the electron state propagates into the magnon spectrum through a cascade of effective interactions. The amplifier doesn't add energy — it restructures the spectrum so the existing energy opens a larger gap.