In a type II superconductor under an external magnetic field, quantized vortices appear. Controlling vortices is important for application of superconductors. Especially, pinning and dynamics of vortices in a dirty superconductor have been studied widely.

Uchiyama et al investigated collective motion of vortices in a type II superconductor using the scanning tunneling microscope[1]. They found that vortex lattice are divided into vortex bundle separated by the glade plane of edge dislocation. In order to investigate origins of this collective motion of vortices, we simulate vortex dynamics in a moderately dirty superconductor using the molecular dynamics method (MD).

The MD is a computer simulation method for many particle dynamics, in which we solve equations of motion of particles numerically. In order to apply this method to the vortex dynamics, we treat vortices as particles in two dimensional space. The equation of motion for* i-*th vortex is given as,

η*(dr _{i})/dt*=

where is

and thermal fluctuation force ffi is given as,

〈

The Lorentz force

We consider 50

[1]K. Uchiyama, S. Suzuki, A. Kuwahara, K. Yamasaki, S. Kaneko, H. Takeya, K. Hirata, N. Nishida; Physica

C, 470 (2010) S795.

Keywords: Molecular Dynamics Method, Vortex Dynamics, Collective Motion, Vortex Pinning