Probing signatures of fractionalization in the candidate quantum spin liquid Cu2IrO3 via anomalous Raman scattering

Long-range entanglement in quantum spin liquids (QSLs) leads to novel low-energy excitations with fractionalized quantum numbers and (in two dimensions) statistics. Experimental detection and manipulation of these excitations present a challenge particularly in view of diverse candidate magnets. A promising probe of fractionalization is their coupling to phonons. Here, we present Raman scattering results for the S = 1/2 honeycomb iridate Cu2IrO3, a candidate Kitaev QSL with fractionalized Majorana fermions and Ising flux excitations. We observe anomalous low-temperature frequency shift and linewidth broadening of the Raman intensities in addition to a broad magnetic continuum, both of which, as we derive, are naturally attributed to the phonon decaying into itinerant Majoranas. The dynamic Raman susceptibility marks a crossover from the QSL to a thermal paramagnet at similar to 120 K. The phonon anomalies below this temperature demonstrate a strong phonon-Majorana coupling. These results provide evidence of spin fractionalization in Cu2IrO3.

Automated summary

Investigated Raman scattering results of S = 1/2 honeycomb iridate Cu2IrO3, observing anomalies and demonstrating strong phonon-Majorana coupling.