Superconducting coherence peak in the electronic excitations of a single   layer cuprate superconductor $Bi_2 Sr_{1.6} La_{0.4} Cu O_{6+\delta}$
  Angle resolved photoemission spectroscopy study is reported on a high quality optimally doped Bi2Sr1.6La0.4CuO6+delta high Tc superconductor. In the antinodal region with maximal d-wave gap, the symbolic superconducting coherence peak, which has been widely observed in multi-CuO2-layer cuprate superconductors, is unambiguously observed in a single layer system. The associated peak-dip separation is just about 19 meV, which is much smaller than its counterparts in multi-layered compounds, but correlates with the energy scales of spin excitations in single layer cuprates. 
J. Wei, Y. Zhang, H. W. Ou, B. P. Xie, D. W. Shen, J. F. Zhao, L. X.   Yang, M. Arita, K. Shimada, H. Namatame, M. Taniguchi...