Probing Flat Band Physics in Spin Ice Systems via Polarized Neutron Scattering*

In this talk we summarize and expand on recent results elucidating how polarized neutron scattering can be used to isolate the correlations of spin modes forming flat bands in pyrochlore magnets. Starting with the nearest-neighbor model of spin ice, we explain why the spin-flip (SF) scattering channel produces pinch point features while the non-spin-flip (NSF) channel produces a completely dispersionless response in the (hhl) scattering plane, a consequence of the fact that the NSF in this plane probes only the modes forming the flat bands. By consider an extended spin ice (ESI) model with further-neighbor interactions, we demonstrate that the NSF is highly sensitive to perturbations lifting the flat band degeneracy, and we use these results to explain the non-flat NSF measured experimentally in the dipolar spin ice compound Ho2Ti2O7.