Magnetic Raman continuum in single-crystalline H3LiIr2O6

Recently H3LiIr2O6 has been reported as a spin-orbital entangled quantum spin liquid (QSL) [K. Kitagawa et al., Nature (London) 554, 341 (2018)], albeit its connection to Kitaev QSL has not been yet identified. To unveil the related Kitaev physics, we perform Raman spectroscopy studies on single-crystalline H3LiIr2O6 samples. We implement a soft chemical replacement of Li+ with H+ from alpha-Li2IrO3 single crystals to synthesize the single crystal samples of the iridate second-generation H3LiIr2O6. The unusual phonon broadening in H3LiIr2O6 implies the random positions of the substituted H+. As well as the lattice dynamics, Raman spectroscopy can also be used to diagnose the QSL state since the magnetic Raman continuum arises from a process involving pairs of fractionalized Majorana fermionic excitation in a pure Kitaev model. We observe a broad dome-shaped magnetic continuum in H3LiIr2O6, in line with theoretical expectations for the two-spin process in the Kitaev QSL. The possible scenario of the structural disordered magnet for the magnetic Raman continuum is also discussed.