FIG. 3.

(a)–(d) The neutron scattering intensities experimentally observed at 5 K are directly compared with the calculated intensities and dispersions discussed in the text. The experimental data on the right panels were integrated over $-5\le l\le 5$. The calculations on the left panels used the best-fitting parameters with $J_c=0$ as discussed in the text, and convoluted by the effective energy resolution of $\delta (ħ\omega )=1.8\text{meV}$ considering the band with along $l$. The displayed cuts are described in (e) within the $(h,k)$ plane. (f) 3D view of the 2D spin-wave excitations of ${\text{CrI}}_3$.