| Abstract: | The core size of a single straight vortex in an extreme type II superconductor is estimated at zero temperature. The free energy is expressed as a non-local functional of the order parameter and vector potential associated with the vortex. Profiles for the order parameter and vector potential that depend on the length scales ξ and λ, respectively, are assumed. For an order parameter profile that achieves its bulk value after the finite distance, ξ, the free energy approximately separates into a sum of two contributions, one depending on the order parameter and the other on the magnetic field. Using two different approximation schemes the two parts of the free energy are minimised. For an order parameter profile that, in its region of change, varies linearly with distance from the vortex axis, the length scale ξ is found to be comparable with the zero temperature coherence length, in agreement with the findings of Ullah et al. (Phys. Rev. B 42 (1990), 9950) for a one-parameter fit to the order parameter. The length scale associated with the magnetic field is also estimated. |
