Honors Thesis Archive
|Title||Probing the Thermal Fluctuations in Bulk YBCO and BSCCO Superconductors|
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|Abstract||High temperature (HTc) superconductors have been studied rigorously for over twenty years because of their potential for both fundamental research and industrial applications, as well as emerging technologies such as smart grids and power transmission. Their unique ability to become superconducting at high temperatures (T > 77K) has ignited much interest in the development of new materials that push the critical temperature, Tc, to ever higher limits. Due to the high transition temperatures, short coherence length, and layered structure, thermal fluctuations near the transition temperature are unusually large. We explore these effects in measurements of the resistivity as a function of temperature in bulk YBCO and BSCCO superconductors using equipment standard in most undergraduate universities. We present a method for converting the measured bulk resistivity into the in-plane resistivity so that the in-plane fluctuation conductivity, Δσab, may be studied as a function of the reduced temperature, ε, in the conventional Gaussian-Ginzburg-Landau model. We observe clear evidence of the onset of thermal uctuations by observing a deviation from linearity of the resistivity with temperature, near the phase transition. Our result in the comparison between theory and experiment for Δσab(ε) is strikingly different than that of Coton et al. We suspect the source of this lie in not-yet-quantifed systematic errors.|