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DOE OSTI · 2586904

Spin correlations in the nematic quantum disordered state of FeSe

Liu, Ruixian [Beijing Normal University (China); Key Laboratory of Multiscale Spin Physics, Beijing (China)] (ORCID:0009000868973972)·Stone, Matthew B. [Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)] (ORCID:0000000178849715)·Gao, Shang [Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)] (ORCID:0000000241987396)·Nakamura, Mitsutaka [J-PARC Center, Japan Atomic Energy Agency (JAEA), Ibaraki (Japan)]·Kamazawa, Kazuya [Research Center for Neutron Science and Technology, Ibaraki (Japan)]·Krajewska, Aleksandra [Rutherford Appleton Laboratory, Didcot (United Kingdom); Max Planck Institute for Solid State Research, Stuttgart (Germany)]·Walker, Helen C. [Rutherford Appleton Laboratory, Didcot (United Kingdom)] (ORCID:0000000278595388)·Cheng, Peng [Renmin University of China, Beijing (China)] (ORCID:0000000323512060)·Yu, Rong [Renmin University of China, Beijing (China)] (ORCID:0000000159361159)·Si, Qimiao [Rice University, Houston, TX (United States)] (ORCID:0000000313572705)·Dai, Pengcheng [Rice University, Houston, TX (United States)] (ORCID:0000000260883170)·Lu, Xingye [Beijing Normal University (China); Key Laboratory of Multiscale Spin Physics, Beijing (China)] (ORCID:0000000204091240)
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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 C 2 symmetry, while Néel spin excitations (Q = (1, 1)) retain C 4 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 3d xy orbital correlations. Modeling the stripe dispersions using a J 1 -K-J 2 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.

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Liu, Ruixian [Beijing Normal University (China); Key Laboratory of Multiscale Spin Physics, Beijing (China)] (ORCID:0009000868973972), Stone, Matthew B. [Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)] (ORCID:0000000178849715), Gao, Shang [Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)] (ORCID:0000000241987396), Nakamura, Mitsutaka [J-PARC Center, Japan Atomic Energy Agency (JAEA), Ibaraki (Japan)], Kamazawa, Kazuya [Research Center for Neutron Science and Technology, Ibaraki (Japan)], Krajewska, Aleksandra [Rutherford Appleton Laboratory, Didcot (United Kingdom); Max Planck Institute for Solid State Research, Stuttgart (Germany)], Walker, Helen C. [Rutherford Appleton Laboratory, Didcot (United Kingdom)] (ORCID:0000000278595388), Cheng, Peng [Renmin University of China, Beijing (China)] (ORCID:0000000323512060), Yu, Rong [Renmin University of China, Beijing (China)] (ORCID:0000000159361159), Si, Qimiao [Rice University, Houston, TX (United States)] (ORCID:0000000313572705), Dai, Pengcheng [Rice University, Houston, TX (United States)] (ORCID:0000000260883170), Lu, Xingye [Beijing Normal University (China); Key Laboratory of Multiscale Spin Physics, Beijing (China)] (ORCID:0000000204091240). 2025-06-05. Spin correlations in the nematic quantum disordered state of FeSe. https://doi.org/10.1038/s41467-025-60071-2

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