Fully gapped single-particle excitations in lightly doped cuprates
/ Authors
K. Shen, T. Yoshida, D. Lu, F. Ronning, N. P. Armitage, W. S. Lee, Xiaoping Zhou, A. Damascelli, D. Feng, N. Ingle
and 16 more authors
H. Eisaki, Y. Kohsaka, H. Takagi, T. Kakeshita, S. Uchida, P. Mang, M. Greven, Y. Onose, Y. Taguchi, Y. Tokura, S. Komiya, Y. Ando, M. Azuma, M. Takano, A. Fujimori, Z. Shen
/ Abstract
The low-energy excitations of the lightly doped cuprates were studied by angle-resolved photoemission spectroscopy. A finite gap was measured over the entire Brillouin zone, including along the d x 2 - y 2 nodal line. This effect was observed to be generic to the normal states of numerous cuprates, including hole-doped La 2 - x Sr x CuO 4 and Ca 2 - x Na x CuO 2 Cl 2 and electron-doped Nd 2 - x Ce x CuO 4 . In all compounds, the gap appears to close with increasing carrier doping. We consider various scenarios to explain our results, including the possible effects of chemical disorder, electronic inhomogeneity, and a competing phase.
Journal: Physical Review B