Abstract
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.
| Original language | English |
|---|---|
| Article number | 5212 |
| Journal | Nature Communications |
| Volume | 16 |
| Issue number | 1 |
| DOIs | |
| State | Published - Dec 2025 |
Funding
The work at Beijing Normal University is supported by National Key Projects for Research and Development of China with Grant No. 2021YFA1400400, the Fundamental Research Funds for the Central Universities and the National Natural Science Foundation of China (grants nos. 12174029 and 11922402) (X.L.). The work at Renmin University of China is supported by the National Science Foundation of China (grants nos. 12334008 and 12174441). P.D. is supported by the U.S. DOE, BES under grant no. DESC0012311 and the Robert A. Welch Foundation under Grant No.C-1839. Q.S. is primarily supported by the U.S. DOE, BES under Award No. DE-SC0018197 and by the Robert A. Welch Foundation Grant No. C-1411. This research used resources at Spallation Neutron Source, a U.S. DOE Office of Science User Facility operated by ORNL. We acknowledge the neutron beam time from J-PARC with Proposal No. 2020B0161. We gratefully acknowledge the Science and Technology Facilities Council (STFC) for access to neutron beam time at ISIS57. The work at Beijing Normal University is supported by National Key Projects for Research and Development of China with Grant No. 2021YFA1400400, the Fundamental Research Funds for the Central Universities and the National Natural Science Foundation of China (grants nos. 12174029 and 11922402) (X.L.). The work at Renmin University of China is supported by the National Science Foundation of China (grants nos. 12334008 and 12174441). P.D. is supported by the U.S. DOE, BES under grant no. DESC0012311 and the Robert A. Welch Foundation under Grant No.C-1839. Q.S. is primarily supported by the U.S. DOE, BES under Award No. DE-SC0018197 and by the Robert A. Welch Foundation Grant No. C-1411. This research used resources at Spallation Neutron Source, a U.S. DOE Office of Science User Facility operated by ORNL. We acknowledge the neutron beam time from J-PARC with Proposal No. 2020B0161. We gratefully acknowledge the Science and Technology Facilities Council (STFC) for access to neutron beam time at ISIS.