Research: Dynamical structure factor of the three-dimensional quantum spin liquid candidate NaCaNi2F7

Spin-wave theory is known to work for ordered magnet, and in particular can be formulated as an expansion in a small parameter, the inverse spin length, 1/S. Both of these are conspicuously absent in the S=1 pyrochlore compound NaCaNi2F7. We argue that here, spin wave theory is an accurate 'short-time' expansion describing the spectrum of disordered ground states which, for this quantity, are statistically equivalent. The (apparent absence of a) role of the small spin remains a mystery.

S. Zhang, H. J. Changlani, K. W. Plumb, O. Tchernyshyov, R. Moessner,
Dynamical structure factor of the three-dimensional quantum spin liquid candidate NaCaNi₂F₇,
Phys. Rev. Lett. 122, 167203 (2019) (arXiv)