Global and Local Measures of the Intrinsic Josephson Coupling in   Tl2Ba2CuO6
  The Intlerlayer Josephson coupling between the planes of Tl2Ba2CuO6 was determined using infrared spectroscopy and magnetic flux vortex imaging. These methods give a consistent value of $\omega_J$= 28 cm$^{-1}$ which, when combined with the condensation energy produces a discrepancy of at least an order of magnitude with deductions based on the interlayer tunneling model. 
A.A. Tsvetkov, D. van der Marel, K.A. Moler, J. R. Kirtley, J. L. de   Boer, A. Meetsma, Z.F. Ren, N. Koleshnikov, D. Dulic,...