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We have fabricated and measured two square two-dimensional Josephson junction arrays, each with 168x168 tunnel junctions. The junctions were made of Al­Al₂O₃­Al, fabricated with standard e­beam lithography and angle evaporation.

The first chip had a room temperature resistance of 27 k per junction and showed a clear Coulomb blockade of approximately 200 µV. Several threshold voltage (V_t) measurements were made on this array, and some statistical analysis of V_t was made with histograms. The threshold voltage showed a periodic dependence on magnetic field with a period corresponding to frustration 1. Additional small peaks, which were periodic with period 0.57 in frustration were also observed, which were most likely due to some second loop size in the design of the arrays. Histograms of 10 000 V_t measurements sometimes displayed two or even three peaks, but only at low temperatures (<100 mK). The distance between those peaks was field dependent, however there was not enough data to determine weather or not it was periodic. The V_t measurements were carried out by ramping voltage over the array. The frequency of these ramps and the voltage where the ramp started, V_s, affected V_t in a complex way.

The second chip had a much lower room temperature resistance of 6.5 k per junction. This sample displayed a Josephson-like behavior with a sharp critical current. There was only a very weak indication of Coulomb blockade at certain magnetic fields and no threshold voltage measurements were made on this chip. Several I vs. V_x and V_y curves were taken at different magnetic fields, where V_x is the normal voltage along the current and V_y is the Hall voltage perpendicular to the current. The zero bias resistance, , could then be calculated as a function of magnetic field. R₀ was periodic with a period corresponding to frustration 1, having dips in the resistance at frustrations 1/2, 1/3 and 2/3. There were some extra peaks as well, at the same frustrations as the peaks in the V_t measurement on the first chip, also having to do with the second loop size. At these peaks the I-V_x and I-V_y curves were discontinuous. The normal current jumped once, and the Hall voltage jumped twice with increasing current. The precise explanation of these jumps is still unknown.

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