Figure 2. Dispersions of the stripe and Néel spin fluctuations in FeSe at 4 and 110 K.

Background-subtracted E–K slice of the spin fluctuations at various incident energies: (a) T=110 K; (b) T=4 K. The data at E≥40 and E≤40 meV were collected on ARCS by using incident energy of 294 and 79 meV, respectively. The isotropic Fe²⁺ magnetic form factor is corrected for both sets of the data. The spectral weight transfer from the Néel (1, 1) to stripe (1, 0) wavevector below ∼70 meV on cooling to 4 K can be clearly seen. The open circles are dispersions obtained from the constant-energy cuts <68 meV in Fig. 3. The colour bar indicates intensity in unit of mbar sr⁻¹ meV⁻¹ f.u.⁻¹. The vertical bars indicate the energy integration range. The horizontal bars at 15 meV indicate the full-width at half-maximum of the Gaussian fittings in Fig. 3i. The horizontal bars at other energies are the errors derived by least-square fittings. The dashed lines are a guide to the eye.