Spectroscopic measurements in model 1D correlated systems offer insights for understanding their two-dimensional counterparts, which include the cuprate and iron pnictide/chalcogenide superconductors. A major challenge is the identification of such correlated systems with dominantly 1D physics. In this Letter, inelastic neutron scattering measurements on ${\mathrm{NaFe}}_{0.53}{\mathrm{Cu}}_{0.47}\mathrm{As}$ single crystal directly reveal quasi-1D spin excitations, resulting from atomic order that leads to magnetic Fe and nonmagnetic Cu chains. The dominant exchange interaction is antiferromagnetic along the chain [$S{J}_{\parallel }\approx 90.1(3)\mathrm{meV}$], whereas the inter-chain couplings are much weaker [$S{J}_{\perp }\approx -2.4(1)\mathrm{meV}$ and $S{J}_{\mathrm{c}}\approx 0.15(5)\mathrm{meV}$]. The quasi-1D spin excitations in ${\mathrm{NaFe}}_{0.53}{\mathrm{Cu}}_{0.47}\mathrm{As}$ stem from both the Néel and stripe vectors, with Néel excitations sensitive to Fe impurities on the Cu site. The spin excitations in quasi-1D ${\mathrm{NaFe}}_{0.53}{\mathrm{Cu}}_{0.47}\mathrm{As}$ and quasi-2D FeSe exhibit a striking resemblance, suggesting a common origin for their coexistent stripe and Néel excitations. Our findings demonstrate magnetic dilution in NaFeAs leads to dimension reduction of its magnetic degree of freedom, presenting a strategy for discovering low-dimensional quantum materials.

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• Spin dynamics
• Strongly correlated systems
• Inelastic neutron scattering
• Neutron scattering