Coexistence of two flux-line species in superconducting slabs

Abstract

Within the London approximation, we show that in anisotropic, strongly type II superconducting slabs two ``species'' of vortices can coexist simultaneously when the external magnetic field is applied at an angle with respect to the crystal principal axes. Simple thermodynamic arguments are used to prove that the appropriate thermodynamic potential is minimum when some of the vortices lie parallel to the c axis while others lie at an angle with respect to the c axis.