Images of interlayer Josephson vortices in TI₂Ba₂CuO(6+δ)

The strength of the interlayer Josephson tunneling in layered superconductors is an essential test of the interlayer tunneling model as a mechanism for superconductivity, as well as a useful phenomenological parameter. A scanning superconducting quantum interference device (SQUID) microscope was used to image interlayer Josephson vortices In TI2Ba2CuO(6+δ) and to obtain a direct measure of the interlayer tunneling in a high-transition temperature superconductor with a single copper oxide plane per unit cell. The measured interlayer penetration depth, λ(c), is ~20 micrometers, about 30 times the penetration depth required by the interlayer tunneling model.