Fluctuation conductivity and the chiral glass state in disordered YBa2Cu3O6+dYBa2Cu3O6+d thin films

• Fluctuation conductivity is experimentally studied in several YBCO thin films.
• The YBCO films were prepared by a chemical deposition method and shows granularity.
• Genuine critical fluctuation regimes were identified.
• The critical regimes are characterized by large exponents.
• The results are interpreted using the chiral-glass superconductor thermodynamics.

In this communication we report on fluctuation conductivity experiments in several superconducting YBa2Cu3O6+dYBa2Cu3O6+d thin films grown by chemical solution deposition. These films are c-axis oriented and show granularity at a submicron scale. Two of the samples were submitted to ion implantation in order to study effects of local disorder. When the temperature approaches the superconducting transition from above we first observe the expected three-dimensional Gaussian fluctuation region. Then, a crossover occurs closely above the transition to a regime dominated by genuine critical fluctuations characterized by a large exponent. Based on previous theoretical predictions, we interpret these critical regimes as precursors of the superconducting chiral glass state.