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

TL;DR

This paper reveals how local frustration in lattice graphs influences magnetic order in itinerant fermions, enabling control over spin arrangements through engineered kinetic frustration, with potential applications in quantum systems.

Contribution

It establishes a general principle linking local frustration centers to magnetic order, extending understanding from simple grids to complex graphs, and proposes a protocol for experimental realization.

Findings

Local frustration centers bind singlets and share delocalized holes.

Magnetic order varies predictably with frustration measures.

The approach enables spatial control of many-body quantum states.

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 a general principle: that local frustration centers bind singlets while sharing a delocalized hole. This collective effect -- absent in exchange magnetism -- extends from rectangular grids to random graphs, producing sharp and predictable variation with tunable frustration measures. Our findings demonstrate that one can shape the spin order and tune the net magnetization by embedding kinetic frustration, opening ways of spatially resolved quantum control of many-body systems. We outline a protocol to realize some of the key findings in existing cold-atom setups.