Raman scattering on spin chains with domain walls in AgCrP₂S₆

Magnetism in one-dimensional systems has been of interest, since it gives rise to various types of non-trivial ground states, such as the Haldane state for integer spins or 1D quantum spin liquid for half-integer spins. In addition, recent predictions for half-integer spins suggest that structural domain walls along a zig-zag antiferromagnetic chain would exhibit a magnetic response through the opening of a gap or the presence of single excitations, detectable in the magnetic Raman spectra [1]. One promising candidate material to observe this effect is AgCrP₂S₆, a van der Waals material containing zig-zag antiferromagnetic spin chains of S = 3/2, Cr³⁺ cations with structural-defect induced domain walls. We synthesized AgCrP₂S₆ and measured the low-frequency Raman scattering response in the temperature range T = 10K-300K. At low temperatures, we observe a broad continuum emerging. A comparison of the continuum with the theoretical predictions for the Raman response of half-integer antiferromagnetic spin chains can be interpreted through four-spinon excitations [2]. However, we have yet to observe any concrete evidence related to the predicted response of domain walls.

[1] Hakani, S., & Kimchi, I. (2024). Crystalline topological defects within response theory. Phys. Rev. B, 109, 224414.

[2] Brenig, W. (1997). Raman scattering from frustrated quantum spin chains. Phys. Rev. B, 56, 2551–2555.