Instability of a tilted vortex line in magnetically coupled layered superconductors

Abstract

We calculate the line tension of a tilted stack of magnetically coupled two-dimensional pancake vortices held at the ends and show that the line tension becomes negative at an angle of 52\ifmmode^\circ\else\textdegree\fi{}. We further calculate the tilt modulus at arbitrary angle \ensuremath{\theta} and show that it becomes negative starting at the same angle 52\ifmmode^\circ\else\textdegree\fi{} for long wavelengths. A structure for the vortex line is given, which is shown to have a lower energy. \textcopyright{} 1996 The American Physical Society.