Pinch point features below the critical temperature in frustrated pyrochlore magnets

Pinch points, sharp anisotropic reciprocal space features appearing in neutron scattering cross sections, are indicative of disordered yet highly correlated spin liquid phases. Recent work has clarified that pyrochlore spin liquid phases can be understood by splitting the degrees of freedom into two separate components, dubbed rotational and irrotational. In particular, it is possible for the irrotational modes to order while the rotational modes fluctuate as a spin liquid, yielding coexistence of Bragg peaks and pinch points in the neutron scattering cross section, a phenomenon dubbed "fragmentation". Inspired by this phenomenon, we show that spin wave fluctuations about ordered configurations can be characterized as "rotational-like" and "irrotational-like" in a number of pyrochlore spin models. We demonstrate how the contributions of these two components can be exposed in neutron scattering measurements and how they combine to produce pinch-point-like features in ordered and non-spin-liquid phases. Our work further clarifies the nature of pinch points and extends the notion of fragmentation as a ubiquitous principle in pyrochlore magnetism.