3D–2D crossover in melting transition on superconducting Mo/Si multilayers

Abstract

Two-dimensional and three-dimensional vortex-lattice melting is observed on superconducting Mo/Si multilayers. Quasi-2D melting takes place in the range of high magnetic fields. The position of the melting transition on H-T phase diagram is in a reasonable quantitative accordance with the existing theories. Above melting line another phase transition is found connected with the decoupling in the liquid phase or with transition from hexatic to ordinary liquid. TAFF regime of the vortex motion is observed in the fluid phase governed by the plastic barrier charateristic for viscous liquid. TAFF regime with different activation energy takes place also in a vortex solid phase above the depinning line.