Tilt instabilities and multiple coexisting vortex orientations in flux-line liquids

Publisher Website
Google Scholar
Abstract
Phase diagrams for various tilt instabilities, as well as phase diagrams for possible coexistence of vortex lines with different orientations in a tilted magnetic field of anisotropic type-II superconductors, are mapped out and compared within anisotropic London theory. Double minima in the Gibbs energy as a function of vortex orientation in the case of noninteracting vortex liquids may be found in a regime of mass anisotropy where long-wavelength tilt instabilities do not occur, and are associated with coexisting species of flux lines of different orientations with respect to the crystal c^ axis. At larger mass-anisotropies, long-wavelength tilt instabilities do occur for tilt modes perpendicular to the ab planes. For tilt modes parallel to the ab planes, instabilities only occur for very large wave numbers, beyond the regime of applicability of London theory. The cutoff dependence on the phase diagrams for the isolated flux-line limit is investigated. It is essential that the elliptic shape of the vortex core is accounted for. When interactions are accounted for in a dense flux-line liquid, the tilt instabilities are removed. © 1996 The American Physical Society.