Anomalous Noise in the Pseudogap Regime of YBCO films.
University of Illinois at Urbana-Champaign
It is widely believed that symmetry-breaking electronic correlations are present in the pseudogap regime of high-Tc superconductors. If such correlations (e.g. stripes) are partially static, one would expect low-frequency noise from thermal switching among different configurations. We have found anomalous noise below a temperature of about 240 K in the normal state of underdoped YBCO and Ca-YBCO films. This noise regime, unlike the more typical noise above 240 K, has features expected for a symmetry-breaking collective electronic state. However, the onset temperature seems to be independent of doping, unlike other pseudogap effects. We speculate on a model involving coupling between stripes and impurities with thermally activated motion.