The Gaussian spin–spin relaxation time T2G, as determined by nuclear magnetic resonance (NMR) spin-echo decay measurements, is found to be useful for diagnosis of quantum critical behaviour in heavy-fermion systems. Combining T2G with the spin–lattice relaxation time T1, the exponent f of the quantity T1T=T 2 2G T is predicted to be sensitive to the type of quantum criticality in the system con...

Using a four fermion interaction Lagrangian, we demonstrate that the spontaneous breaking of vector symmetries requires the existence of a light (comparing with the heavy fermion mass) scalar particle and the low energy effective theory (the σ model) obtained after integrating out heavy fermion degrees of freedom is asymptotically a renormalizable one. When applying the idea to the electroweak ...