Browsing by Author "Lin, P. J."

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Magnetic phase diagram of type-II superconductors: From high T-c to low T-c superconductors
(2008-09-15)
Li, D.
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Lin, P. J.
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Rosenstein, B.
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電子物理學系
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Department of Electrophysics
Phase diagram of both high temperature superconductors and low temperature superconductors are studied within the Ginzburg-Landau approach. Due to enhanced thermal fluctuation strength, disorder effects are relatively small in high T-c superconductors and consequently can be studied analytically. The vortex glass transition line is different and well separated from both the melting line and from the so-called second peak lines. On contrary, in low temperature superconductors, the disorder effect is dominant, as the thermal fluctuation strength is very small. Peak effect appears due to cross over of the collective pinning region to stronger pinning region. The location of the peak effect is obtained. The disorder and thermal fluctuation effects on structure phase transition are also studied. (C) 2008 Elsevier B.V. All rights reserved.
Superconducting fluctuations and the Nernst effect in high-T-c superconductors
(2013-10-01)
Chen, Y-J
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Lin, P. J.
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Wu, K. H.
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Rosenstein, B.
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Luo, C. W.
The comprehensive rho(T) measurements and the consequent resistivity curvature mapping (RCM) on Y0.7Ca0.3Ba2Cu3O7-delta thin films (doping levels p = 0.08-0.21) elucidate a phase diagram for the whole doping range. This phase diagram further strengthens a view that the 'normal' phase in hole-doped cuprates should be divided into a strong superconducting (SC) fluctuation phase and the 'real' normal phase in which there is no significant influence of SC. The temperature of superconducting fluctuations T-f as a function of p was calculated using the Ginzburg-Landau model for layered superconductors. Comparisons between T-f and the Nernst temperature establish the origin of the Nernst effect as SC fluctuations. Some of the details in rho(T) cannot be fully understood by the existing models and call for a more sophisticated theory of carrier dynamics in cuprates.
Theory of the fluctuation diamagnetism of strongly layered superconductor in strong magnetic field
(2009)
Lin, P. J.
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Zhuravlev, V.
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Li, D.
;
Rosenstein, B.
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電子物理學系
Recent experiments in Bi(2)Sr(1)Ca(1)Cu(2)O(8+delta) [7] demonstrated that the fluctuation diamagnetism in strong magnetic field at the vicinity of the critical temperature significantly differs from the behavior predicted by fluctuation diamagnetism theories based on Ginzburg-Landau model within the lowest Landau level approximation. In this study, we extend previous theoretical result to the T < T(c) region and incorporate to the theory contributions from higher Landau levels. Comparison with experimental results shows a good agreement with the theory for an optimally doped sample, while for under-doped sample the agreement is poor at low temperature.