Quasiparticle spectroscopy and high-field phase diagrams of cuprate   superconductors -- An investigation of competing orders and quantum   criticality
  We present scanning tunneling spectroscopic and high-field thermodynamic studies of hole- and electron-doped (p- and n-type) cuprate superconductors. Our experimental results are consistent with the notion that the ground state of cuprates is in proximity to a quantum critical point (QCP) that separates a pure superconducting (SC) phase from a phase comprised of coexisting SC and a competing order, and the competing order is likely a spin-density wave (SDW). The effect of applied magnetic field, tunneling current, and disorder on the revelation of competing orders and on the low-energy excitations of the cuprates is discussed. 
N.-C. Yeh, C.-T. Chen, V. S. Zapf, A. D. Beyer, C. R. Hughes, M.-S.   Park, K.-H. Kim, and S.-I. Lee