Simple analytical model of vortex-lattice melting in two-dimensional superconductors

Article

关键词: II SUPERCONDUCTORS;    FLUX-LATTICE;    PERTURBATION-SERIES;    TRANSITION;    KAPPA-(BEDT-TTF)(2)CU(NCS)(2);    FLUCTUATIONS;    BEHAVIOR;    VORTICES;    LIQUID;    ORDER;   

DOI  :  10.1103/PhysRevB.60.4277

来源: SCIE

【 摘 要 】

The melting of the Abrikosov vortex lattice in a two-dimensional (2D) type-II superconductor at high magnetic fields is studied analytically within the framework of the phenomenological Ginzburg-Landau theory. It is shown that local phase fluctuations in the superconducting order parameter, associated with low-energies sliding motions of Bragg chains along the principal crystallographic axes of the vortex lattice, lead to a weak first-order melting transition at a certain temperature T-m, well below the mean-field T-c, where the shear modulus drops abruptly to a nonzero value. The residual shear modulus above T-m decreases asymptotically to zero with increasing temperature. Despite the large phase fluctuations, the average positions of Bragg chains at finite temperature correspond to a regular vortex lattice, slightly distorted with respect to the triangular Abrikosov lattice. It is also shown that a genuine long-range phase coherence exists only at zero temperature; however, below the melting point the vortex state is very close to the triangular Abrikosov lattice. A study of the size dependence of the structure factor at finite temperature indicates the existence of quasi-long-range order with S((G) over right arrow) similar to N-sigma, and 1/2 < sigma < 1, where superconducting crystallites of correlated Bragg chains grow only around pinning chains. This finding may suggest a very efficient way of generating pinning defects in quasi-2D superconductors. Our results for the melting temperature and for the entropy jump agree with the state-of-the-art Monte Carlo simulations. [S0163-1829(99)08129-1].

【 授权许可】

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