STRUCTURE OF AN ISOLATED VORTEX IN AN ANISOTROPIC TYPE-II SUPERCONDUCTOR

The Ginzburg-Landau equations with general effective-mass anisotropy are diagonalized for a general direction v of an isolated vortex core. For v not parallel to one of the three crystal axis directions, the local magnetic induction b contains components b and b , perpendicular to v, which vanish as 2 away from the center of the core with coefficients that are odd in the azimuthal angle . In the London limit far from the core, b and b are comparable to b3=v^b, and all fall off exponentially in , with two distinct exponents, each of which depends explicitly upon the azimuthal angle about v. The presence of b and b reduces the energy cost of the locking of the core into the lattice but does not remove it entirely, as the leading correction to the line energy is proportional to the parameter 2 (rather than ), where is the parameter introduced previously by the author. With the use of an ansatz, an exact form for the field components and reduced order parameter f in the core region is obtained. The lines of constant b3 and b 0 in the core region are found for arbitrary effective-mass anisotropy and v. These forms should be observable by scanning tunneling microscopy and by large-momentum-transfer neutron-scattering experiments for fields slightly greater than Hc1. In addition, the angular dependence of Hc1 should exhibit a kink, as the vortex cores prefer to lie along one of the crystal symmetry directions. © 1990 The American Physical Society.