μSR and NMR studies on the van der Waals cluster magnet Nb₃Cl₈

The van der Waals cluster magnet Nb₃Cl₈ has recently been shown to possibly host a quantum-spin-liquid ground state. The Nb ions in this compound form a breathing kagome structure, where the magnetic moment comes from three nearest Nb ions forming a molecular cluster with spin 1/2. Previous bulk measurements including magnetic susceptibility and specific heat suggested the existence of spinon Fermi surfaces. Here we further probe the spin system by nuclear magnetic resonance (NMR) and muon spin rotation and relaxation (μSR) techniques. We confirm that there is no magnetic long-range order and the dynamical spin fluctuations persist down to 0.075 K. These results provide further evidence that Nb₃Cl₈ may host a quantum spin liquid.