Spin liquid like Raman signatures in hyperkagome iridate Na${}_4$Ir${}_3$O${}_8$

Combining Raman scattering measurements with mean field calculations of the Raman response we show that Kitaev-like magnetic exchange is dominant in the hyperkagome iridate Na${}_4$Ir${}_3$O${}_8$. In the measurements we observe a broad Raman band at $\sim$~3500 cm${}^{-1}$ with a band-width $\sim 1700$~cm${}^{-1}$. Calculations of the Raman response of the Kitaev-Heisenberg model on the hyperkagome lattice shows that the experimental observations are consistent with calculated Raman response where Kitaev exchange interaction ($J_K$) is much larger than the Heisenberg term J${}_1$ ($J_1\mathrm{/}{J}_K\sim 0.1$). A comparison with the theoretical model gives an estimate of the Kitaev exchange interaction parameter.