Abstract Body

For application of type Ⅱ superconductors, controlling vortices is important. For example, pinning of vortices is needed for higher critical current, and manipulation of the vortex is needed for a quantum computer. For the pinning of vortices, slanted or splayed columnar defects are effective.[1] Also, the splayed columnar defects cause an anomalous peak effect.

In order to investigate these properties of vortices in the superconductor with splayed columnar defects, we use three-dimensional molecular dynamics (3D-MD) method[2].

In 3D-MD, three dimensional superconductors are divided into two-dimensional layers. We solve equations of motion of each vortex in each layer.

We include the force by the external current \( f \begin{subarray}{rl} d \\ i,l \end{subarray} \) , the interaction force between the vortices \( f \begin{subarray}{rl} VV \\ i,l \end{subarray} \) , the fluctuation force due to heat \( f \begin{subarray}{rl} f \\ i,l \end{subarray} \) , the pinning force due to defects \( f \begin{subarray}{rl} imp \\ i,l \end{subarray} \) , the bending force of the vortices \( f \begin{subarray}{rl} b \\ i,l \end{subarray} \) , and the force from the external magnetic field \( f \begin{subarray}{rl} M \\ i,l \end{subarray} \) in the equations of motion. In this model, we have introduced a three-dimensional pinning force. Figure shows a examples of columnar defects, and distribution of vortices obtained by this simulation using this method. We investigate field dependence of the critical current and the origin of the peak effect.

References

[1] A. Park, S. Pyon, K. Ohara, N. Ito, and T. Tamegai, Phys. Rev. B 97,064516(2018)
[2]C. J. Olson, R. T. Scalettar, G. T. Zimányi, and N. Grønbech-Jensen, Phys. Rev. B 62, R3612(R) (2000)

Acknowledgment

We would like to thank T. Tamegai for giving us useful advice related to experimental results of critical current.

Figure. Columnar defects (a) and distribution of vortices (b)

Keywords: Vortex, 3D-Molecular dynamics, Critical current, Peak effect