Scanning Tunneling Spectroscopic Studies of Cuprate Superconductors
  Quasiparticle tunneling spectra of both hole-doped (p-type) and electron-doped (n-type) cuprates are studied using a low-temperature scanning tunneling microscope. The results reveal that neither the pairing symmetry nor the pseudogap phenomenon is universal among all cuprates, and that the response of n-type cuprates to quantum impurities is drastically different from that of the p-type cuprates. The only ubiquitous features among all cuprates appear to be the strong electronic correlation and the nearest-neighbor antiferromagnetic Cu^{2+}-Cu^{2+} coupling in the CuO_2 planes. 
N.-C. Yeh, C.-T. Chen, R.P. Vasquez, C.U. Jung, S.-I. Lee, K. Yoshida,   and S. Tajima