Spinons and damped phonons in spin-1/2 quantum-liquid Ba$_{4}$Ir${}_3$O${}_{10}$ observed by Raman scattering

TL;DR

This study uses Raman scattering to identify signatures of spinons and damped phonons in a potential spin-orbit quantum liquid Ba4Ir3O10, revealing insights into quantum liquid behavior and phonon-spin interactions.

Contribution

It provides experimental evidence of spinon signatures and phonon damping in a spin-orbit quantum liquid candidate using Raman scattering techniques.

Findings

Detection of a broad Raman hump consistent with spinon excitations

Observation of strong phonon damping due to spin-phonon coupling

Absence of these features in the magnetically ordered phase

Abstract

In spin-1/2 Mott insulators, non-magnetic quantum liquid phases are often argued to arise when the system shows no magnetic ordering, but identifying positive signatures of these phases or related spinon quasiparticles can be elusive. Here we use Raman scattering to provide three signatures for spinons in a possible spin-orbit quantum liquid material Ba${}_4$Ir${}_3$O${}_{10}$: (1) A broad hump, which we show can arise from Luttinger Liquid spinons in Raman with parallel photon polarizations normal to 1D chains; (2) Strong phonon damping from phonon-spin coupling via the spin-orbit interaction; and (3) the absence of (1) and (2) in the magnetically ordered phase that is produced when 2% of Ba is substituted by Sr ((Ba${}_{0.98}$Sr${}_{0.02}$)${}_4$Ir${}_3$O${}_{10}$). The phonon damping via itinerant spinons seen in this quantum-liquid insulator suggests a new mechanism for enhancing thermoelectricity in strongly correlated conductors, through a neutral quantum liquid that need not affect electronic transport.