Response of a Doped Mott Insulator to a Local Charge: Implications for Muon Spin Resonance

A charged impurity (such as a muon) in a metal induces a charge inhomogeneity which screens the electric field of the impurity and may also cause the spin fluctuation spectrum near the impurity to differ from that of thebulk. Doped Mott insulators (such as the high Tc copper-oxide superconductors are believed to be) present a particularly delicate case: the Mott correlations suppress the charge response, but also increasethe sensitivityof magnetic propertiesto changesinthe charge density. Here we summarize the implications of recent dynamical mean field calculations for this physics.