GLOBAL AND LOCAL MEASURES OF THE INTRINSIC JOSEPHSON COUPLING IN TL2BA2CUO6 AS A TEST OF THE INTERLAYER TUNNELING MODEL

One leading candidate theory of high-temperature superconductivity in the copper oxide systems is the interlayer tunnelling (ILT) mechanism( 1). In this model, superconductivity is created by tunnelling of elect ron pairs between the copper oxide planes-contrasting with other model s in which superconductivity first arises by electron pairing within e ach plane. The ILT model predicts that the superconducting condensatio n energy is approximately equal to the gain in kinetic energy of the e lectron pairs due to tunnelling. Both these energies can be determined independently(2-4), providing a quantitative test of the model. The g ain in kinetic energy of the electron pairs is related to the interlay er plasma frequency, omega(J), of electron pair oscillations, which ca n be measured using infrared spectroscopy. Direct imaging of magnetic flux vortices also provides a test(5), which is performed here on the same samples. In the high-temperature superconductor Tl2Ba2CuO6, both the sample-averaging optical probe and the local vortex imaging give a consistent value of omega(J) approximate to 28 cm(-1) which, when com bined with the condensation energy produces a discrepancy of at least an order of magnitude with deductions based on the ILT model.