VORTEX-LATTICE VORTEX-LIQUID STATES IN ANISOTROPIC HIGH-TC SUPERCONDUCTORS

We investigate vortex-lattice structures in highly anisotropic superconductors for a situation where the vortices are slightly inclined with respect to the easy plane of the crystal. The equilibrium configuration is found to be a vortex lattice with a rhombic unit cell highly compressed along the direction perpendicular to the easy plane. The elastic modulus for a shear deformation along this direction is exponentially small, which should result in melting of the vortex lattice, already at quite low temperatures. We discuss the implications of our theoretical results for experiments on the angular dependence of the torque for anisotropic high-T(c) superconductors in an applied magnetic field.