Vortex fluctuations, tilt modulus and resistivity of layered high- Tc superconductors

Abstract

We investigate the influence of the layered structure of high- T c superconductors on the tilt modulus and on flux line melting and calculate the voltage-current relation in a magnetic field near the Kosterlitz-Thouless temperature T KT . The tilt modulus depends on the magnetic and Josephson interlayer coupling energy. For a single flux line with a local distortion, the magnetic contribution is a factor ( d/ λ) 2 and the Josephson contribution a factor m/ M smaller than in an isotropic continuum. Here, d is the interlayer spacing, λ the London penetration depth in the ab-planes, and M and m are the electron masses in c- and ab-directions, respectively. A flux line lattice with the lattice constant a o ⩾2 λ melts at the temperature T KT at which independent point-like vortex-antivortex pairs dissociate. For sufficiently large fields, the exponents a( T), of the voltage-current relation V∼ I a( T) , and b(T), of the voltage-field relation V∼ H b( T) for I→0, are connected by b( T) = a( T)/2.