Year: 2024
Type: preprint
Abstract: The unusual quantum-disordered magnetic ground state intertwined with superconductivity and electronic nematicity in FeSe has been a research focus in iron-based superconductors. However, the intrinsic spin excitations across the entire Brillouin zone in detwinned FeSe, which forms the basis for a microscopic understanding of the magnetic state and superconductivity, remain to be determined. Here, we use inelastic neutron scattering to map out the spin excitations of FeSe dewtinned with a uniaxial-strain device. We find that the stripe spin excitations (Q=(1, 0)/(0, 1)) exhibit the $C_2$ symmetry up to $E\approx120$ meV, while the N{é}el spin excitations (Q=(1, 1)) retain their $C_4$ symmetry in the nematic state. The temperature dependence of the difference in the spin excitations at Q=(1, 0) and (0, 1) for temperatures above the structural phase transition unambiguously shows the establishment of the nematic quantum disordered state. The similarity of the Néel excitations in FeSe and NaFeAs suggests that the Néel excitations are driven by the enhanced electron correlations in the $3d_{xy}$ orbital. By determining the key features of the stripe excitations and fitting their dispersions using a Heisenberg Hamiltonian with biquadratic interaction ($J_1$-$K$-$J_2$), we establish a spin-interaction phase diagram and conclude that FeSe is close to a crossover region between the antiferroquadrupolar, Néel, and stripe ordering regimes. The results provide an experimental basis for establishing a microscopic theoretical model to describe the origin and intertwining of the emergent orders in iron-based superconductors.
Source: arXiv (Cornell University)
Authors: Liu, Ruixian, Stone, Matthew B., Gao, Shang, Nakamura, Mitsutaka, Kamazawa, Kazuya, Krajewska, Aleksandra, Walker, Helen C., Cheng, Peng, Yu, Rong, Si, Qimiao, Dai, Pengcheng, Lu, Xingye
Institutions: Beijing Normal University, Oak Ridge National Laboratory, Japan Atomic Energy Agency, Japan Proton Accelerator Research Complex, Comprehensive Research Organization for Science and Society, CROSS Neutron Science and Technology Center, Rutherford Appleton Laboratory, Renmin University of China, Rice University
Language: English
Field: Materials Science
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W4390810444