Recently, Professor Lu Xingye' s Team from the School of Physics and Astronomy at Beijing Normal University, in collaboration with their partners, use inelastic neutron scattering (INS) to obtain clear intrinsic spin-excitation spectrum of FeSe across the entire Brillouin zone (BZ), enabled by a newly designed low-background uniaxial-strain detwinning device and careful background determination from an empty device. This research titled "Spin correlations in the nematic quantum disordered state of FeSe" has been published in Nature Communications.

The abstract of the paper is as follows:

The quantum-disordered state in FeSe, intertwined with superconductivity and nematicity, has been a research focus in iron-based superconductors. However, the intrinsic spin excitations across the entire Brillouin zone in detwinned FeSe, crucial for understanding its magnetism and superconductivity, have remained unresolved. Using inelastic neutron scattering, we reveal that stripe spin excitations (Q = (1, 0)/(0, 1)) exhibit the C2 symmetry, while Néel spin excitations (Q = (1, 1)) retain C4 symmetry within the nematic state. Temperature-dependent differences between Q = (1, 0) and (0, 1) spin excitations above the structural transition unambiguously reveals the nematic quantum disordered state. Comparison with NaFeAs suggests the Néel excitations originate from enhanced 3dxy orbital correlations. Modeling the stripe dispersions using a J1-K-J2 Heisenberg Hamiltonian, we establish a spin-interaction phase diagram, positioning FeSe near a crossover regime between the antiferroquadrupolar, Néel, and stripe orders. Our results provide key insights into the microscopic spin interactions and their role in the intertwined orders in iron-based superconductors.

Reference：https://www.nature.com/articles/s41467-025-60071-2