Magnetic Field Driven Quantum Phase Transitions in Josephson Arrays
  We have studied the magnetic-field-driven quantum phase transitions in Josephson junction arrays with a large coordination number. The characteristic energies were extracted in both the superconducting and insulating phases by integrating the current-voltage characteristics over a voltage range 2eV\leqk_B T. For the arrays with a relatively strong Josephson coupling, we observed duality between the energies in the superconducting and insulating phases. The arrays with a weaker Josephson coupling demonstrate an intermediate, "bad metal" regime in weak magnetic fields; this observation underlines the importance of vortex pinning at large scales and, presumably, emergent inhomogeneity in the presence of strong offset charge disorder. 
J. Paramanandam, M.T. Bell, L.B. Ioffe, and M.E. Gershenson
cond-mat.dis-nn cond-mat.supr-con