Nuclear magnetic and quadrupole resonance studies of the stripes materials

Nuclear Magnetic and Quadrupole Resonance (NMR/NQR) is a powerful tool to probe electronic inhomogeneities in correlated electron systems. Its local character allows for probing different environments due to spin density modulations or inhomogeneous doping distributions emerging from the correlations in these systems. In fact, NMR/NQR is not only sensitive to magnetic properties through interaction of the nuclear spin, but also allows to probe the symmetry of the charge distribution and its homogeneity, as well as structural modulations, through sensitivity to the electric field gradient (EFG). We review the results of NMR and NQR in the cuprates from intrinsic spatial variations of the hole concentration in the normal state to stripe order at low temperatures, thereby keeping in mind the influence of doping induced disorder and inhomogeneities. Finally, we briefly discuss NQR evidence for local electronic inhomogeneities in the recently discovered iron pnictides, suggesting that electronic inhomogeneities are a common feature of correlated electron systems.

► NMR/NQR evidence for inhomogeneities and stripe order in the cuprates is reviewed.
► Some kind of pinning potential is always necessary to observe a static charge order.
► The hole distribution determined by NMR ranges from 0.025 in YBCO up to 0.06 in LSCO.
► Extrinsic disorder by doping may turn on intrinsic disorder in the CuO2 planes.
► NQR evidence for electronic inhomogeneities has also been found in the iron pnictides.