Raman scattering in quasi-one-dimensional antiferromagnets

The experimental search for quantum spin liquids can often be hampered by misidentification of low-dimensional spinons. Spinons in two-dimensions can be topological in nature and hint at long range entanglement. Spinons in one-dimension, namely in the S=1/2 Heisenberg chain, are denied such features. Thus, detection of one-dimensional spinons can be viewed as strong experimental eveidence against a topological quantum spin liquid state. We show that such spinons arising from one-dimensional physics leave a clear fingerprint in magnetic Raman scattering. We achieve this by calculating the magnetic Raman intensity of coupled Heisenberg chains within a first order perturbative theory for different lattice geometries. We find that the quasi-one-dimensional Raman intensity is highly structured and polarisation dependent, with a characteristic sharp peak that is associated with the emergent 'triplon' quasiparticle. Detection of the triplon indicates a 'dimensional reduction' whereby the excitations of a two-dimensional system are manifestly one-dimensional. Our findings for the anisotropic triangular lattice are in excellent agreement with recent magnetic Raman scattering measurements on the anisotropic triangular antiferromagnet Ca₃ReO₅Cl₂. Extending our method to the anisotropic honeycomb and Kagome lattices is a challenging task that may assist in diagnosing quantum disorder in such systems.