Shaping Magnetic Order by Local Frustration for Itinerant Fermions on a Graph

Abstract: Kinetic magnetism is an iconic and rare example of collective quantum order that emerges from the interference of paths taken by a hole in a sea of strongly interacting fermions. Here the lattice topology plays a fundamental role, with odd loops frustrating ferromagnetism, as seen in recent experiments. However, the resulting magnetic order on a general graph has remained elusive. Here we systematically establish, using exact diagonalization, that local frustration centers on a grid strongly bind singlets while sharing a delocalized hole. This collective effect generalizes to random graphs, producing sharp and predictable variation with tunable frustration measures. Our findings demonstrate that one can shape the spin order as well as tune the net magnetization by embedding geometric frustration, opening up new avenues for spatially resolved quantum control of many-body systems. We outline a protocol to realize some of the key findings in existing cold-atom setups.