First-order vortex lattice phase transition in (La1-xSrx)2CuO4 single crystals:: Universal scaling of the transition lines in high-temperature superconductors

The first-order vortex-lattice phase transition was observed in (La1-xSrx)(2)CuO4 single crystals (0.046 less than or equal to x less than or equal to 0.077). A scaling law, H-pt(T)[Oe] = 2.85 gamma(-2)s(-1)(T-c/T - 1), was found to universally hold for the phase transition lines not only in the present system but also in YBa2Cu3Ogamma, and Bi2Sr2CaCu2Ogamma. Here gamma(2) and a are the anisotropy factor and the superconducting layer spacing. This remarkable scaling provides sound evidence that the first-order phase transition in high-T-c, superconductors manifests itself as the vortex-lattice sublimation rather than melting.