Multiple coexisting orientations of flux lines in superconductors with uniaxial anisotropy

The self-energy and Gibbs free energy of rigid vortex lines are calculated for a uniaxially anisotropic London superconductor with a magnetic field applied at an angle φ from the c^ axis. When the correct elliptical core cutoff is used, the Gibbs free energy may have degenerate double minima as a function of vortex orientation. This indicates the coexistence of flux lines with different orientations at fields just above ${\mathit{H}}_{\mathit{c}1}$, applied at an angle φ≠0 from the c^ axis. The regime of parameters H, φ, ${\mathit{M}}_{\mathit{z}}$/M, and κ where this occurs is mapped out.