We report single-crystal neutron spectroscopy and bulk characterization on hydrothermally grown Nd2Sn2O7, revealing a dynamical moment fragmentation embedded within the all-in-all-out ordered state. The spectra show a nearly flat band with pinch-point-like momentum dependence, accompanied by dispersive branches that generate half-moon features across multiple Brillouin zones. These defining signatures are captured quantitatively by a minimal dipolar-octupolar spin Hamiltonian, demonstrating excellent agreement between experiment and theory. The higher flat-mode energy helps account for the absence of dynamical interference in prior muon spin relaxation (muSR) studies, while the lack of any photon-like excitation imposes strict constraints on the proposed Coulombic antiferromagnet scenario. Our results extend dynamical moment fragmentation to Nd2Sn2O7 and identify it as a clean, tractable platform for quantitative exploration of emergent gauge-field physics and multipolar spin-wave dynamics in frustrated magnets.
Cite
@article{arxiv.2510.04845,
title = {Dynamical moment fragmentation in the all-in all-out pyrochlore Nd2Sn2O7},
author = {Yi Luo and Matthew S. Powell and Joseph A. M. Paddison and Brenden R. Ortiz and J. Ross Stewart and Joseph W. Kolis and Adam A. Aczel},
journal= {arXiv preprint arXiv:2510.04845},
year = {2026}
}
Comments
5 pages, 4 figures, 1 table in main text; 11 pages, 6 figures, 2 tables in SM. v3 (05/04/2026, published version): Clarified moment fragmentation and multipolar spin-wave interpretation; added discussion of sample dependence, {\mu}SR dynamical window, and observed energy shift (SM). v2 (12/11/2025): Expanded heat-capacity analysis