The combination of nanostructure and correlated systems has been an interesting field in the frontier of condensed matter physics. Exploring and understanding the physical properties of correlated electron materials with reduced dimensionalities is the focus of this study. For this purpose, we fabricated thin flakes of calcium ruthenate (Ca3Ru2O7) and iron telluride (Fe1+yTe) with various thickness via mechanical exfoliation and characterized their magneto-electronic transport properties. The two materials are chosen for their rich phase transitions in structure, conductivity and magnetic orders.The electronic transport properties of exfoliated Ca3Ru2O7 flakes have been investigated as a function of thickness. We find that flakes thinner than 10 nm are more insulating and show drastic changes in magnetoresistance and metal-insulator transitions. A possible scenario might be enhanced RuO6 octahedral distortion due to the loss of apical oxygen atoms on the cleaved surfaces. This may play a more significant role in thinner flakes as the surface-to-volume ratio increases. The study establishes a control of ruthenate properties by dimensionality and connects the fields of two-dimensional materials and correlated electron systems.In Fe1+yTe exfoliated-flake devices we find the first-order structural phase transition in Fe1+yTe bulk becomes broadened in flakes with an intermediate thickness accompanying a superconducting-like dip below 10K. Further reducing the thickness of the flakes wipes out all features, and the flakes behaves like a highly-disordered two-dimensional system exhibiting charge-localized states with largely enhanced MR ratio. The behavior can be well described by Mott's variable range hopping regime, with a localization length ~10 nm which may originate from the excess iron atoms.One of the future goals of this project is the carrier doping on exfoliated thin flakes (gating effect) using either solid high-κ dielectric or ionic liquid. Another goal will be exploring more perovskite type materials since our unique exfoliation method may be the only choice to mechanically cleave the layered structured crystals with strong interlayer binding force to date. Characterization of the structure of exfoliated flakes will be also an important work to further verify the origin of exotic behaviors of the flakes.
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