Critical exponents of frustrated Josephson junction arrays (JJA)

We present a reanalysis of the experimental data obtained at Delft in niobium and aluminum square JJA in magnetic fields B = Φ0f/p2, with Φ0 = h/2e, lattice spacing p ∼ 10μm, f = 0, 1/2, and the ''irrational'' √(5-3/2)∼0.38. Above the critical temperature τc the linear normal state resistance is fitted, using different statistical tests, to the form R/RN = Ae-B/(τ-τc)ν. For τ < τc the data is fitted to the nonlinear resistance V ∼ Ia(τ). We find that the best fits to the data give the critical exponents ν(f = 0) = 0.5, ν(f = .38) ∼ 0.55, while for f = 1/2 we can not distinguish between ν = 1/2 or 1/3. The jump in a(τ = τc) gives 2η=[a(τc)-1]-1 of 1/4 and 0.19, for f = 0 and 1/2, respectively. The results for f = 1/2 compare well with recent theoretical predictions. For f = 0.38, a(τ) has no jump and decreases monotonically as τ → τc. (orig.)