Quantum criticality in a uranium heavy fermion system revealed with NMR spin-spin relaxation

In order to clarify quantum criticality in heavy fermion systems, we propose to use the Gaussian spin-echo decay rate 1/T2G of the NMR spin-spin relaxation. In contrast to the spin-lattice relaxation rate 1/T1, which is connected with the dynamical susceptibility Imχ(q,ω), I/T2G is driven by the static susceptibility Reχ(q,0) at finite q for an antiferromagnet. The combined quantity T1T/T22G is found to provide key information in determining the nature of quantum criticality. The T-dependence of T1T/T22G for the Sn site in the heavy fermion compound USn3 is presented as an example.