Determination of vortex motion characteristics, effective thickness and dynamic resistance in very thin YBaCuO bilayer structures

In order to develop superconducting flux flow devices, we have measured the electrical characteristics of microbridges made from bilayers comprised of a conductive capping layer deposited on a very thin YBa2Cu3O7-delta film. In the flux creep regime, these structures show a low and quasi-constant de pinning-to-critical current ratio and a high maximum vortex velocity. As ex pected from these features, the microbridges can be driven in the flux flow regime in the vicinity of T-c. In the flux flow regime, surprisingly, the dynamic resistance is not an increasing function of temperature and shows a value which is in the range of the normal-state resistance at the onset of the superconductive transition.