Quasi-one-dimensional spin excitations in the iron pnictide NaFe${}_{0.53}$Cu${}_{0.47}$As

Abstract

Spectroscopic measurements in model one-dimensional (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 work, inelastic neutron scattering measurements on NaFe${}_{0.53}$Cu${}_{0.47}$As single crystal directly reveal quasi-1D spin excitations, resulting from atomic order that lead to magnetic Fe and nonmagnetic Cu chains. The dominant exchange interaction is antiferromagnetic along the chain ($S{J}_{\parallel }\approx 90.1(3)$~meV), whereas the inter-chain couplings are much weaker ($S{J}_{\perp }\approx -2.4(1)$~meV and $S{J}_{\mathrm{c}}\approx 0.15(5)$~meV). The quasi-1D spin excitations in NaFe${}_{0.53}$Cu${}_{0.47}$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 NaFe${}_{0.53}$Cu${}_{0.47}$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.

supplementary information available upon request