Time-Resolved Neutron Scattering Investigation of Spin Dynamics in Ho₂Ti₂O₇

Spin-ice materials such as Ho₂Ti₂O₇ host a macroscopically degenerate manifold dictated by the “two-in/two-out” ice rule, supporting emergent monopole excitations that govern the magnetic dynamics at low temperatures. Despite extensive static and frequency-domain studies, microscopic insights into the correlated nature of the time-dependent responses of magnetic monopoles remain underexplored experimentally. Here, we employed a magnetic-field-pump, neutron-probe technique to extend neutron scattering into the time domain by measuring S(Q, t) to directly track spin-spin correlations with sub-microsecond resolution at sub-Kelvin temperatures. With the pumping magnetic field applied within the scattering plane, our results document time- and momentum-dependent signatures deep in the spin-ice regime, which suggests a field-induced transfer of magnetic spectral weight across the momentum space at relevant timescales. In addition, we performed simulations of S(Q, t) employing Monte Carlo methods and the SU(N)NY package to compare the temporal spin correlations with the characteristics observed in the neutron scattering spectrum.