  Anyonic excitations emerging from a Kitaev spin liquid can form a basis for
quantum computers. Searching for such excitations motivated intense research on
the honeycomb iridate materials. However, access to a spin liquid ground state
has been hindered by magnetic ordering. Cu2IrO3 is a new honeycomb iridate
without thermodynamic signatures of a long-range order. Here, we use muon spin
relaxation to uncover the magnetic ground state of Cu2IrO3. We find a
two-component depolarization with slow and fast relaxation rates corresponding
to distinct regions with dynamic and static magnetism, respectively. X-ray
absorption spectroscopy and first principles calculations identify a mixed
copper valence as the origin of this behavior. Our results suggest that a
minority of Cu2+ ions nucleate regions of static magnetism whereas the majority
of Cu+/Ir4+ on the honeycomb lattice give rise to a Kitaev spin liquid.
