Quantum Fisher Information in semiclassical magnon systems

Quantum Fisher Information (QFI) is a powerful spectroscopic tool to witness many-body quantum entanglement in solid state materials, but it is not always obvious how to relate it to other condensed matter quantities. In this study we examine simple theoretical spin systems in the semiclassical context and highlight QFI as a quantity that reflects the degree of quantum superposition in a system. We further show examples of when emergent quantum phases are approached, QFI diverges across multiple wave vectors. QFI is therefore not only helpful as a lower bound for entanglement depth, but serves as a unique momentum-resolved probe of entanglement that offers a novel perspective on quantum critical phenomena.