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Abstract Charge modulations have been widely observed in cuprates, suggesting their centrality for understanding the high- T c superconductivity in these materials. However, the dimensionality of these modulations remains controversial, including whether their wavevector is unidirectional or bidirectional, and also whether they extend seamlessly from the surface of the material into the bulk. Material disorder presents severe challenges to understanding the charge modulations through bulk scattering techniques. We use a local technique, scanning tunneling microscopy, to image the static charge modulations on Bi 2− z Pb z Sr 2− y La y CuO 6+ x . The ratio of the phase correlation length ξ CDW to the orientation correlation length ξ orient points to unidirectional charge modulations. By computing new critical exponents at free surfaces including that of the pair connectivity correlation function, we show that these locally 1D charge modulations are actually a bulk effect resulting from classical 3D criticality of the random field Ising model throughout the entire superconducting doping range. 

Abstract Vanadium Dioxide (VO₂) is a material that exhibits a phase transition from an insulating state to a metallic state at ≈68 °C. During a temperature cycle consisting of warming followed by cooling, the resistivity of VO₂changes by several orders of magnitude over the course of the hysteresis loop. Using a focused laser beam (λ = 532 nm), it is shown that it is possible to optically generate micron‐sized metallic patterns within the insulating phase of a VO₂planar junction which can be used to tune, on demand, the resistance of the VO₂junction. A resistor network simulation is used to characterize the resulting resistance drops in the devices. These patterns persist while the base temperature is held constant within the hysteretic region while being easily removed totally by simply lowering the base temperature. Surprisingly, it is also observed that the pattern can be partially erased using an atomic force microscope (AFM) tip on the submicron scale. This erasing process can be qualitatively explained by the temperature difference between the VO₂surface and the tip which acts as a local cooler. This optical and AFM resistive fine‐tuning offers the possibility of creating controllable synaptic weights between room‐temperature VO₂neuristors.