Browsing by Author "Jiang, Xujiang"

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Concurrent intersection point of magnetization and magnetoconductivity curves in strongly fluctuating superconductors
(2017-12-20)
Chi, Cheng
;
Jiang, Xujiang
;
Wang, Jiangfan
;
Li, Dingping
;
Rosenstein, Baruch
The thermal fluctuations contribution to magnetization and magnetoconductivity of type-II layered superconductors is calculated in the framework of the Lawrence-Doniach model. For numerous high-temperature cuprate superconductors, it was discovered that the magnetization dependence on temperature in a wide range of fields exhibits an intersection point at a temperature slightly below Tc. We notice a similar intersection point of the magnetoconductivity curves at the approximate same temperature. The phenomenon is explained by strong (non-Gaussian) thermal fluctuations with interactions treated using a self-consistent theory. All higher Landau levels should be included. Dimensionality of the fluctuations is defined, and the two- to three-dimensional crossover is the key for the existence of intersection points.
Strong thermal fluctuations in cuprate superconductors in magnetic fields above T-c
(2014-02-18)
Jiang, Xujiang
;
Li, Dingping
;
Rosenstein, Baruch
;
電子物理學系
;
Department of Electrophysics
Recent measurements of fluctuation diamagnetism in high-temperature superconductors show distinct features above and below T-c, which can not be explained by simple Gaussian fluctuation theory. Self-consistent calculation of magnetization in layered high-temperature superconductors, based on the Ginzburg-Landau-Lawrence-Doniach model and including all Landau levels is presented. The results agree well with the experimental data in a wide region around T-c, including both the vortex liquid below T-c and the normal state above T-c. The Gaussian fluctuation theory significantly overestimates the diamagnetism for strong fluctuations. It is demonstrated that the intersection point of magnetization curves appears in the region where the lowest Landau level contribution dominates and magnetization just below T-c is nonmonotonic. Our calculation supports the phase disordering picture of fluctuations above T-c.