Fractional spin excitations in the infinite-layer cuprate CaCuO$_2$

Abstract

We use resonant inelastic x-ray scattering (RIXS) to investigate the magnetic dynamics of the infinite-layer cuprate CaCuO2. We find that close to the ( 1 /2, 0) point the single magnon decays into a broad continuum of excitations accounting for ∼ 80% of the total magnetic spectral weight. Polarization resolved RIXS spectra reveal the overwhelming dominance of spin-flip (∆S = 1) character of this continuum with respect to the ∆S = 0 multimagnon contributions. Moreover, its incidentenergy dependence is identical to that of the magnon, supporting a common physical origin. We propose that the continuum originates from the decay of the magnon into spinon pairs, and we relate it to the exceptionally high ring exchange Jc ∼ J1 of CaCuO2. In the infinite layer cuprates longrange and multi-site hopping integrals are very important and amplify the 2D quantum magnetism effects in spite the 3D antiferromagnetic Néel order.I.

Emergence of spinons in layered trimer iridate Ba4Ir3O10

“…QSLs in higher dimensions are harder to identify, but hold promise for realizing novel topological order and intrinsic long-range quantum entanglement with potential applications in quantum information [16,17]. Several studies have provided evidence for spinons in twodimensional (2D) or three-dimensional (3D) systems such as triangular, Kagome, Kitaev honeycomb, or pyrochlore lattices [18][19][20][21][22][23], while definitive material-realization remains controversial and is a major target of research. Another possible approach relies on 1D systems as building blocks to realize higher-dimensional QSL states [24], which, however, is less explored.…”