Magnetic oscillations of critical current in Josephson-junction stacks

We consider magnetic oscillations of critical current in stacks of Josephson junctions, which are realized in mesas fabricated from layered high-temperature superconductors. Depending on the stack lateral size and magnetic field, oscillations may have either period of half flux quantum per junction (large-size regime) or one flux quantum per junction (small-size regime). We study in detail the crossover between these two regimes. In the small-size regime the lattice structure experiences periodic series of phase transitions between aligned rectangular configuration and triangular configuration. Triangular configurations in this regime realize only in narrow regions near magnetic-field values corresponding to integer number of flux quanta per junction. This work was supported by the U.\ S.\ DOE, Office of Science, under contract \# W-31-109-ENG-38.