Instabilities in the Flux Line Lattice of Anisotropic Superconductors

Abstract

The stability of the flux line lattice has been investigated within anisotropic London theory. This is the first full-scale investigation of instabilities in the `chain' state. It has been found that the lattice is stable at large fields, but that instabilities occur as the field is reduced. The field at which these instabilities first arise, $b^{\ast }(\epsilon ,\theta )$, depends on the anisotropy $\epsilon$ and the angle $\theta$ at which the lattice is tilted away from the $c$-axis. These instabilities initially occur at wavevector $k^{\ast }(\epsilon ,\theta )$, and the component of $k^{\ast }$ along the average direction of the flux lines, $k_z$, is always finite. As the instability occurs at finite $k_z$ the dependence of the cutoff on $k_z$ is important, and we have used a cutoff suggested by Sudb\ospace and Brandt. The instabilities only occur for values of the anisotropy $\epsilon$ appropriate to a material like BSCCO, and not for anisotropies more appropriate to YBCO. The lower critical field $H_{c_1}(\varphi )$ is calculated as a function of the angle $\varphi$ at which the applied field is tilted away from the crystal axis. The presence of kinks in $H_{c_1}(\varphi )$ is seen to be related to instabilities in the equilibrium flux line structure.

Extensively revised paper, with modified analysis of elastic instabilities. Calculation of the lower critical field is included, and the presence of kinks in $H_{c_1}$ is seen to be related to the elastic instabilities. 29 pages including 16 figures, LaTeX with epsf style

References in corpus (1)

• The Flux-Line Lattice in Superconductors

Cited by in corpus (6)

• The London theory of the crossing-vortex lattice in highly anisotropic layered superconductors
• Vortex-chain phases in layered superconductors
• Vortex Matter Transition in Bi${}_2$Sr${}_2$CaCu${}_2$O${}_{8+y}$ under Tilted Fields
• Stripe Domains and First Order Phase Transition in the Vortex Matter of Anisotropic High-temperature Superconductors
• Flux Line Lattices in Artificially Layered Superconductors
• Tilted and crossing vortex chains in layered superconductors