On the origin of reentrance in 2D Josephson Junction Arrays

A comparative study of the magnetic properties of shunted and unshunted two-dimensional Josephson junction arrays (2D-JJA) is presented. Using a single-plaquette approximation of the 2D-JJA model, we were able to successfully fit all our experimental data (for the temperature, AC and DC field dependencies of susceptibility) and demonstrate that the dynamic reentrance of AC susceptibility is directly linked to the value of the Stewart-McCumber parameter \beta_C. Based on extensive numerical simulations, a phase diagram \beta_C vs \beta_L is plotted which demarcates the border between the reentrant and non-reentrant behavior in the arrays.