Quantifying ground state degeneracy in planar artificial spin ices: the magnetic structure factor approach

Magnetic structure factor (MSF) is employed to investigate the ground state degeneracy in rectangular-like artificial spin ices. Our analysis considers the importance of nanoislands size via dumbbell model approximation. Pinch points in MSF and residual entropy are found for rectangular lattices with disconnected nanoislands, signalizing an emergent gauge field, through which magnetic monopoles interact effectively. Dipole-dipole interaction is also used and its predictions are compared with those obtained by dumbbell model.