Negative magnetoresistance slope in superconducting granular films

• The theory explaining recently observed negative magneto-resistance slope in ultra-thin YBa2Cu2O7−δ films is developed.
• Considering film as an array of the Josephson junctions, we solve the sine-Gordon equations including a viscosity term.
• The solution yields a negative magneto-resistance slope setting in agreement with the experimental results.

A phenomenological theory is developed to explain the recently observed negative magnetoresistance slope in ultra-thin granular YBa2Cu2O7−δ films. Viewing this system as a two-dimensional array of extended Josephson junctions, we numerically solve the sine-Gordon equations including a viscosity term that increases linearly with the external field. The solution yields a negative magnetoresistance slope setting in at a field that is determined by the geometry and thus independent of temperature, in agreement with the experimental results.