Superconducting phase transitions in frustrated Josephson-junction arrays on a dice lattice
arXiv:0811.4675 · doi:10.1016/j.physc.2008.07.004
Abstract
Transport measurements are carried out on dice Josephson-junction arrays with the frustration index and 1/2 which possess, within the limit of the model, an accidental degeneracy of the ground states as a consequence of the formation of zero-energy domain walls. The measurements demonstrate that both the systems undergo a phase transition to a superconducting vortex-ordered state at considerably high temperatures. The experimental findings are in apparent contradiction with the theoretical expectation that frustration effects in the system are particularly strong enough to suppress a vortex-ordering transition down to near zero temperature. The data for are more consistent with theoretical evaluations. The agreement between the experiments and the Monte Carlo simulations of a model for suggests that the order-from-disorder mechanism for the removal of an accidental degeneracy may still be effective in the system. The transport data also reveal that the dice arrays with zero-energy domain walls experience a much slower critical relaxation than other frustrated arrays only with finite-energy walls.
4 pages, 4 figures