London penetration depth in the tight binding approximation: orthorhombic distortion andoxygen isotope effects in cuprates

Abstract

We present a simple derivation of an expression for the superfluid density in superconductors with the tight binding energy dispersion. The derived expression isdiscussed in detail because of its distinction from the known expressions for ordinarysuperconductors with parabolic energy dispersion. We apply this expression for theexperimental data analysis of the isotope effect in London penetration depth parameterλ in the BiSrCuO and YBaCuO family compounds near optimal doping, taking intoaccount the orthorhombic distortion of crystal structure, and estimate the isotopicchange of hopping parameters from the experimental data. We point out that1/λ2 temperature behaviour is very sensitive to the ratio2Δm(T = 0)/kBTc and estimate this quantity for a number of compounds.