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 competition between vortex-vortex interactions and pinning interactions makes simulation of the system a computationally intensive many-body problem. We are using molecular dynamics and Monte Carlo simulations to study these systems.
We have developed a novel hybrid Monte Carlo method to study phase transitions and vortex pinning in these materials, which requires considerably less computing power than regular Monte Carlo methods.

An understanding of the vortex state and its pinning is crucial in our endeavours to develop superior superconducting materials in collaboration with experimentalists in the Physics department of the University of Southampton.

Monte-Carlo simulations of a layered high temperature superconductor

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, 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, SJ, 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