A critical value in the product of the anisotropy parameter and the magnetic field is observed in interlayer Josephson-vortex systems by extensive Monte Carlo simulations. Below (above) this critical value the thermodynamic phase transition between the normal and the superconducting states upon temperature sweeping is first (second) order. It is discussed that the origin of this tricritical point is the highly anisotropic layered structure of high- $T_c$ superconductors.

• Received 11 February 2000

DOI:https://doi.org/10.1103/PhysRevLett.85.2577