Magnetic dilution in the triangular lattice antiferromagnet NaYb${}_{1-x}$Lu${}_x$O${}_2$

The delafossite-like compound NaYbO${}_2$ hosts a triangular lattice of Yb${}^{3+}$ moments and is a promising candidate for the realization of a quantum spin liquid ground state – an exotic, quantum-disordered magnetic phase featuring long-range entanglement of spins. Tuning this system away from this quantum-disordered regime toward classical order or spin freezing is a powerful approach to shed light on the nature of the parent ground state. Here we leverage the substitution of nonmagnetic Lu${}^{3+}$ onto the Yb${}^{3+}$ sites to study the effects of magnetic disorder in NaYbO${}_2$ using low-temperature ac susceptibility, heat capacity, and muon spin relaxation ($\mu$SR) measurements. Our $\mu$SR measurements reveal resilient, correlated magnetic fluctuations that persist to at least 15% dilution, precluding conventional spin freezing and magnetic inhomogeneity. Heat capacity and magnetic susceptibility resolve a rapid suppression of the field-induced ``up-up-down’’ magnetic order upon dilution and a crossover in the power-law behavior of the low-temperature magnetic excitations associated with the zero-field quantum disordered ground state. Taken together, these results support the notion of a robust network of entangled moments in NaYbO${}_2$, and provides experimental validation of several models of a Heisenberg triangular lattice antiferromagnet in the presence of disorder.