Fig. 4. The spatial configuration of fluctuations changes in each cooldown.
(a) Susceptibility maps repeated at the same location on sample S1 at 0.78Tc, taken between temperature cycles. The island configuration changes dramatically after a temperature cycle well above Tc (between the two top images, I and II). Successive images at the same conditions (2 bottom images, II and III) are overall similar, but there are visible changes in the position of the streaks around the puddle which indicates their dynamic nature. Each scan contains 13k pixels with pixel size of 120X120 nm2. Data acquisition per pixel is 45 ms. Scale bars 3 μm. (b) STD vs. T plots. Both red curves are taken in the same location (extracted from the data in panel (a)) before and after cycling above Tc. The difference in the curves represent the spatial configuration of islands that reorganizes with each cycle above Tc. The green and black curves are taken at different locations on the sample, 150 and 250 μm away from the area presented in (a). The multi-peak curve structure is created by puddles that became active at different temperatures and present complex shapes and non-trivial temperature evolution. (c) χ vs. T plots vary between locations on the sample and reveal a non-monotonic temperature evolution of χ in sample S1. Blue and pink curves were taken at the location marked in (a). The yellow curve was taken in a different location, hundreds of microns away. The black, green and purple curves are taken on different locations in sample S3. Away from the QCP, these curves overlap showing no difference in the chi signal between different locations. Value for S3 multiplied by 0.8 to fit in the same scale as the data for S1. (d) Characteristic time of events vs. T, for the black data set in (b), recorded with the time resolution of 10 ms. Each characteristic time and standard deviation bars are extracted from an individual time trace (inset) or from streaks in a specific image. Event times vary between milliseconds to minutes and display a non-monotonic temperature dependence, with a complex, multi-peak profile. The purple data point is taken from sample S3. In sample S3, away from the critical point these events appear only near Tc.