Anomalous Noise in the Pseudogap Regime of YBa$_{2}$Cu$_{3}$O$_{7-\delta }$*

The pseudogap regime of high temperature superconductors is usually associated with electronic correlations (e. g. charge stripes). In symmetry-broken correlated systems, slow switching between different configurations contributes to low-frequency noise. Transport noise measurements performed in underdoped YBCO and Ca-doped YBCO thin films reveals a well-defined temperature of order 250K below which an extra noise component sets in that exhibits sensitivity to magnetic fields, aging effects, and large discrete fluctuators. Such effects are characteristic of noise from collective states in disordered systems. The noise onset temperature varies with measurement frequency but is only weakly doping-dependent. To explain this behavior, we speculate on a model involving thermally-activated motion of charge stripes partially pinned to underlying magnetic order.