Emergence of a Fluctuating Ground State in Y-Kapellasite under Pressure

Y-kapellasite [Y₃Cu₉(OH)₁₉Cl₈], which hosts an original anisotropic kagome sublattice, is a promising candidate for studying elusive and complex correlated physics. It exhibits a theoretically predicted in-plane (1/3; 1/3) magnetic order [Hering et al., npj Comput. Mater. 8, 1 (2022)], but its magnetic interaction values place it close to a phase boundary to a spin liquid state [Chatterjee et al., Phys. Rev. B 107, 125156 (2023)]. 

Our μSR measurements under hydrostatic pressure demonstrate the complete suppression of static magnetism in favor of a fully dynamical ground state at 2.3 GPa. Complementary high-pressure x-ray and optical phonon measurements reveal a gradual reduction of the kagome anisotropy, enhancing magnetic frustration without structural transitions. Our results establish Y-kapellasite as a rare clean kagome model in which long-range order is suppressed by pressure-tuned frustration, the first fingerprint for the realization of a quantum spin liquid without strong disorder.