Confinement of fractional excitations in the 3D Kitaev magnet β-Li₂IrO₃

Kitaev quantum spin liquid (QSL) is a highly frustrated state in topological magnets with excitations from fractional particles. In candidate materials like RuCl₃ and A₂IrO₃(A = Na, Li), there is always an ordered state below Tc. However, the transition from spin liquid like fractional excitations to the magnons of the ordered state is still unclear. Here, we report the Raman scattering result on three-dimensional magnet β-Li₂IrO₃. We identified the polarization and temperature dependence of the magnons and fractional excitations in Raman. This provides first direct evidence for confinement of fractional excitations into magnons in a kitaev system, which so far has only been observed in quasi-1d systems.