Dirac spinons intermingled with singlet states in the random kagome antiferromagnet YCu3(OD)6+xBr3-x (x=0.5)

We elucidate the ground state nature and low-energy spin dynamics of the s=1/2 near-perfect kagome antiferromagnet YCu3(OD)6+xBr3-x (x=0.5) using Cu63 nuclear quadrupole resonance (NQR) and muon spin relaxation/rotation (μSR) techniques. Our combined Cu63 NQR and μSR data, along with the inverse Laplace transform analysis, reveal an inhomogeneous ground state comprising the majority of a gapless spin liquid intermingled with a minor fraction of spin singlets with varying energy gaps. Furthermore, the Cu63 NQR relaxation rate evinces distinct signatures of Dirac spinons, featuring a power-law dependence of 1/T1∼Tη with η=1.35 at temperatures below 0.13J (≅8K). Our results demonstrate that a kagome lattice endowed with specific exchange randomness provides a prominent platform for exploring Dirac fermions in magnetic insulators.