  The nature of multipolar order and hyperfine-enhanced (HE) $^{141}$Pr nuclear
spin dynamics in PrV$_2$Al$_{20}$ was investigated using the muon spin
relaxation technique. No explicit sign of time-reversal symmetry breaking was
found below the multipolar order temperature $T_Q\sim 0.6$ K in a zero applied
field as anticipated on the basis of the antiferroquadrupolar (AFQ) order
picture proposed by Sakai and Nakatsuji [J. Phys. Soc. Jpn. 80, 063701 (2011)].
Further evidence of the nonmagnetic ground state was obtained from the
observation of HE $^{141}$Pr nuclear spin fluctuations in the MHz scale. A
marked increase in the muon spin-lattice relaxation rate (1/$T_{\rm 1,\mu}$)
was observed below 1 K with decreasing temperature, which was attributed to the
perturbation on the HE $^{141}$Pr nuclear spin dynamics associated with the
development of AFQ correlations. The longitudinal field dependence of 1/$T_{\rm
  1,\mu}$ revealed that the enhanced $^{141}$Pr nuclear spin accidentally has
an effective gyromagnetic ratio close to that of the muon.

Strongly Correlated Electrons