Three-dimensional to two-dimensional crossover in layered high-Tc superconductors

Abstract

We calculate vortex lattice properties in a highly anisotropic layered high-Tc superconductor using Monte Carlo simulations. The superconducting order parameter is expanded in products of lowest Landau level states in the ab plane and tight-binding Bloch states in the c direction. The phase diagram is then a universal function of a dimensionless effective temperature scrT and effective interlayer coupling η, both of which depend on temperature T and magnetic field B. We characterize the vortex lattice by the helicity modulus (superfluid density) Υ in the c direction, and shear modulus μ in the ab plane. There appears to be no phase transition separating two-dimensional (2D) and 3D solids. Instead, the 3D to 2D transition is manifested by a smooth crossover of Υ from nearly mean-field 3D behavior Υ∼η at large η, to a 2D, fluctuation-dominated regime Υ∼η2 at small η. In the limit η→0 the shear modulus smoothly approaches a finite value characteristic of a purely 2D vortex lattice. We discuss the possibility that this dimensional crossover may account for the disappearance of the neutron scattering peaks in BiSr2Ca2CuO8+δ at high fields.

Source-reported materials — not catalogue approval

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