Molecular Dynamics Simulations on Melting Transition of Vortex Lattices in Mesoscopic Superconductors

Because of weak pinning and strong thermal and quantum fluctuations in cuprate high-Tc superconductors, there is a melting line of a vortex lattice in the H-T phase diagram. Recently, Ooi et al. showed the melting temperature in a mesoscopic superconducting cuprate square plate oscillates with increasing magnetic field. They explained this oscillation comes from the stability of configurations of n² vortices (n=1, 2, 3, ...) [1]. In order to confirm this explanation, we study the vortex lattice melting in a mesoscopic superconductor, using the molecular dynamics method [2,3]. Temperature dependence is included in the thermal fluctuation force and the penetration depth in the vortex-vortex interaction. In order to determine the melting point, we use the standard deviation of time development of vortex positions. We have found that melting temperature oscillates with increasing vortex number [4]. Also, we will show how vortex lattices melt.
[1] S. Ooi, T. Mochiku, M. Tachiki, and H. Hirata, Phys. Rev. Lett. 114, 087001 (2015).
[2] D. E. Fujibayashi, M. Kato, Physica C 484, 94 (2013).
[3] M. Kato, D. E. Fujibayashi, Physics Procedia 45, 133 (2013).
[4] M. Kato, H. Kitago, J. Physics: Conf. Series 871(2017) 012028.