A High-Temperature Superconductor consists of copper oxide planes and is penetrated by thin tubes carrying magnetic flux. The intersection of the planes and the flux gives rise to circulating supercurrents known as vortices. Electric transport currents cause a Lorentz force to act on vortices and any resulting drift of the vortices will produce a voltage across the superconductor and hence dissipation. Fortunately, vortices can be pinned, for instance by atomic impurities or defects in the material. The long-range interaction between the vortices make simulations of the system a computationally intensive many-body problem.
We are using molecular dynamics (MD) techniques to integrate the coupled differential equations of motion for the system, which allow us to investigate the dynamics of the system in the presence of a Lorentz force, temperature and a pinning potential.

Using Molecular Dynamics, we have investigated the dynamic phases of the vortex state in the presence of random pinning. This area of research has recently attracted much attention, and our results confirm the existence of the predicted moving Bragg glass and moving transverse glass phases.

A snapshot of vortices (blue spheres) travelling in the viewing directions through a random pinning potential (green surface).
See Animation below

Papers

Refereed Journal Papers

Price, A.R., Fangohr, H, Cox, S.J., and De Groot, P.A.J. (2000) Monte Carlo Simulation of Layered High Temperature Superconductors. Physica C, 341-348 p.1303-1304.

Fangohr, H., Price, A.R., Cox, S.J., De Groot, P.A.J., Daniell, G.J., Thomas, K.S. 2000. Efficient Methods for handling Long-Range forces in Particle-Particle Simulations. J Computational Physics, 162, 372-384.

Fangohr, H., De Groot, P.A.J., and Cox, S.J. 2001 Critical Transverse Forces in Weakly Pinned Driven Vortex Systems, Phys Rev B 63 064501.

Fangohr, H., Cox, S.J., and De Groot, P.A.J., 2001 Vortex dynamics in two-dimensional systems at high driving forces. Physical Review B., 64 p.064505.

Refereed & Presented Conference Papers

Price, A.R., Fangohr, H., Cox, S.J., De Groot, P.A.J., 1999. Computational Modelling of High Temperature Superconductors. Superconductivity Group Annual Conference (Institute of Physics), 31st March, Uni of Birmingham, Birmingham, UK. 300-301

Price, A.R., Cox, S.J., De Groot, P.A.J., 2000. Monte Carlo Simulation of Layered High Temperature Superconductors. Houston 2000 High Temperature Superconductivity Conference.

Conference Contributions - other

Fangohr, H., Cox, S.J., De Groot, P.A.J., 2000. Talk (H Fangohr). Molecular dynamics simulation studies of driven vortex systems in the presence of a transverse force. Max-Planck Institut fuer Physik komplexer Systeme, Dresden, Germany. Feb 2000 International Workshop on Microscopic Structure and Dynamics of Vortices in Unconventional Superconductors and Superfluids.

Fangohr, H., Dodgson, M.J., De Groot, P.A.J., and Cox, S.J. (2001) Computer simulation studies of a layered pancake system using the substrate model. Invited poster presentation at VIII. Vortex Workshop, in Bariloche, Argentina

Fangohr, H., Koshelev, A.E., Dodgson, M.J., De Groot, P.A.J., and Cox, S.J. (2002) Numerical simulation of the substrate model for pancake vortices in a layered superconductor. Oral presentation at March Meeting American Physical Society, 2002, Indianapolis, USA.

Fangohr, H., Dodgson, M.J., De Groot, P.A.J., and Cox, S.J. (2002) Computer simulation studies of layered pancake systems using the substrate model. Poster presentation at combined Condensed Matter and Materials Physics Conference 2002, Brighton, UK.

Animation