  In the Kitaev magnet $\alpha$-RuCl$_3$, the existence of a
magnetic-field-induced quantum spin liquid phase and of anyonic excitations are
discussed controversially. We address this elusive, exotic phase via
helicity-dependent Raman scattering and analyze the Raman optical activity of
excitations as a function of magnetic field and temperature. The hotly debated
field regime between 7.5 T and 10.5 T is characterized by clear spectroscopic
signatures such as a plateau of the Raman optical activity of the dominant,
chiral spin-flip excitation. This provides direct evidence for the existence of
a distinct intermediate field regime compatible with a quantum spin liquid
phase.
