Browsing by Author "Zhuravlev, V."

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Dynamics of disordered type-II superconductors: Peak effect and the I-V curves
(2007-09-01)
Bel, G.
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Li, D. P.
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Rosenstein, B.
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Vinokur, V.
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Zhuravlev, V.
We quantitatively describe the competition between the thermal fluctuations and disorder by the Ginzburg-Landau approach using both the replica method in statics and the dynamical Martin-Siggia-Rose approach which allows generalization beyond linear response. The two methods are consistent in static, while the dynamical method allows calculation of the critical current as function of magnetic field and temperature. The surface in the J-B-T space defined by this function separates between a dissipative moving vortex matter regime and vortex glass. The non-Ohmic I-V curve is obtained. (c) 2007 Elsevier B.V. All rights reserved.
Elastic properties of the Abrikosov lattice near the upper critical field and peak effect in the critical current
(2008-02-15)
Rosenstein, B.
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Zhuravlev, V.
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電子物理學系
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Department of Electrophysics
Abrikosov vortices in type II superconductors under magnetic field form highly correlated configurations with well defined elasticity, like regular atomic solids. While in the London limit vortices can be considered as line-like objects, when the field approaches the upper critical field H-c2(T) the core structure becomes important for elastic properties. Taking into account the deformation of the shape of the current distribution leads to significant increase in the shear modulus of the vortex lattice compared to previous estimates. The elastic properties determine the response to vortex matter pinning. The modified value of the elastic modulus is used to support a recent theory of the discontinuous "peak effect" in the critical current. It is argued that the critical current of the vortex lattice decreases monotonously as a function of the magnetic field, jumping to a high value in the homogeneous amorphous phase. (c) 2007 Published by Elsevier B.V.
Quantitative theory of transport in vortex matter of type-II superconductors in the presence of random pinning
(2007-07-01)
Rosenstein, B.
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Zhuravlev, V.
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交大名義發表
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電子物理學系
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National Chiao Tung University
We quantitatively describe the competition between interactions, thermal fluctuations, and random quenched disorder using the dynamical Martin-Siggia-Rose approach [Phys. Rev. A 8, 423 (1973)] to the Ginzburg-Landau model of the vortex matter. The approach first used by Dorsey [Phys. Rev. B 45, 523 (1992)] to describe the linear response far from H-c1 is generalized to include both pinning and finite voltage. It allows one to calculate the non-Ohmic I-V curve, thereby extending the theory beyond the linear response. The static flux line lattice in type-II superconductors undergoes a transition into three disordered phases: the vortex liquid (not pinned), the homogeneous vortex glass (pinned, if one disregards an exponentially small creep at finite temperatures), and the crystalline Bragg glass (pinned) due to both thermal fluctuations and disorder. The location of the glass transition line in the homogeneous phase is determined and compared to experiments. The line is clearly different from both the melting line and the second peak line describing the translational and rotational symmetry breaking at high and low temperatures, respectively. Time correlation and response functions of the order parameter as functions of the time difference are calculated in both the liquid and the amorphous homogeneous phases. They determine the relaxation properties of the vortex matter due to the combined effect of pinning and thermal fluctuation. We calculate the critical current as a function of magnetic field and temperature in the homogeneous phase. The surface in the J-B-T space defined by this function separates between a dissipative moving vortex matter regime and vortex glass. A quantitative theory of the peak effect, qualitatively different from the conventional one due to Pippard.
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.
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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.
Vortex lattice in type II superconductors under magnetic field in the presence of inhomogeneities
(2008-04-01)
Rosenstein, B.
;
Shapiro, B. Ya.
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Zhuravlev, V.
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電子物理學系
;
Department of Electrophysics
We investigate the structure, elastic and dynamical properties of the vortex matter in the presence of artificially created or intrinsic gradients of the critical temperature in the framework of the Ginzburg-Landau theory. The region of parameters in which vortex cores are not well separated is treated perturbatively in 1 - H-c2(T)IHc2(0). Critical current for periodic pinning potential is obtained and general expressions for elastic moduli at long wavelength are derived. We show that it is impossible to restrict the system to lowest Landau level. We use it to provide a theory of the discontinuous peak effect in critical current which appears near H-c2(T) line in low T-c strongly type II superconductors. Influence of thermal fluctuations is also considered and we find softening of the shear modulus in the vicinity of vortex lattice melting line. (c) 2008 Elsevier B.V. All rights reserved.