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First-Order Melting and Dynamics of Flux Lines in a Model for YBa$_2$Cu$_3$O$_{7-δ}$

Seungoh Ryu·D. Stroud
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Abstract

We have studied the statics and dynamics of flux lines in a model for YBCO, using both Monte Carlo simulations and Langevin dynamics. For a clean system, both approaches yield the same melting curve, which is found to be weakly first order with a heat of fusion of about $0.02 k_BT_m$ per vortex pancake at a field of $50 {\rm kG}.$ The time averaged magnetic field distribution experienced by a fixed spin is found to undergo a qualitative change at freezing, in agreement with NMR and $μ{\rm SR}$ experiments. Melting in the clean system is accompanied by a proliferation of free disclinations which show a clear B-dependent 3D-2D crossover from long disclination lines parallel to the c-axis at low fields, to 2D ``pancake'' disclinations at higher fields. Strong point pins produce a logarithmical $\ln t$ relaxation which results from slow annealing out of disclinations in disordered samples.

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Seungoh Ryu, D. Stroud. 1996-05-16. First-Order Melting and Dynamics of Flux Lines in a Model for YBa$_2$Cu$_3$O$_{7-δ}$. https://doi.org/10.1103/physrevb.54.1320

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