The correlation between the Nernst effect and fluctuation diamagnetism in strongly fluctuating superconductors
نویسنده
چکیده
We study theNernst effect influctuating superconductors by calculating the transport coefficient xy a in a phenomenologicalmodel where the relative importance of phase and amplitude fluctuations of the order parameter is tuned continuously to smoothly evolve from an effectiveXYmodel to themore conventional Ginzburg–Landau description. To connect with a concrete experimental realizationwe choose themodel parameters appropriate for cuprate superconductors and calculate xy a and the magnetization M over the entire range of experimentally accessible values offield, temperature and doping.We argue that xy a and M are both determined by the equilibriumproperties of the superconducting fluctuations (and not their dynamics) despite the former being a transport quantity. Thus, the experimentally observed correlation between theNernst signal and themagnetization arises primarily from the correlation between xy a and M. Further, there exists a dimensionless ratio T M xy a ( ) that quantifies this correlation.We calculate, for thefirst time, this ratio over the entire phase diagramof the cuprates andfind it agrees with previous results obtained in specific parts of the phase diagram.We conclude that there appears to be no sharp distinction between the regimes dominated by phase fluctuations andGaussian fluctuations for this ratio in contrast to xy a and M individually. The utility of this ratio is that it can be used to determine the extent towhich superconducting fluctuations contribute to theNernst effect in different parts of the phase diagram given themeasured values ofmagnetization.
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تاریخ انتشار 2017