Continuum of magnetic excitations in the Kitaev honeycomb iridate D${}_3$LiIr${}_2$O${}_6$

Abstract

Inelastic neutron scattering (INS) measurements of powder D${}_3{(}^7$Li)(${}^{193}$Ir)${}_2$O${}_6$ reveal low energy magnetic excitations with a scattering cross section that is broad in $|Q|$ and consistent with a Kitaev spin-liquid (KSL) state. The magnetic nature of the excitation spectrum is demonstrated by longitudinally polarized neutron studies. The total magnetic moment of 1.7(2)$\hat{I}{¼}_B$/Ir inferred from the total magnetic scattering cross section is consistent with the effective moment inferred from magnetic susceptibility data and expectations for the $J_{\mathrm{eff}}=1/2$ single ion state. The rise in the dynamic correlation function $\mathcal{S}(Q,\ddot{I}‰)$ for $\hslash \ddot{I}‰<5$meV can be described by a nearest-neighbor Kitaev model with interaction strength $K\approx -13(5)$~meV. Exchange disorder associated with the mixed D-Li site could play an important role in stabilizing the low $T$ quantum fluctuating state.

5 pages, 4 figures