Study of HgBa$_2$CuO$_{4+\delta}$ by Angle-Resolved Photoemission   Spectroscopy
  We present the first angle-resolved photoemission measurement on the single-layer Hg-based cuprate, HgBa$_2$CuO$_{4+\delta}$ (Hg1201). A quasi-particle peak in the spectrum and a kink in the band dispersion around the diagonal of the Brillouin zone are observed, whereas no structure is detected near the Brillouin zone boundary. To search for a material-dependent trend among hole-doped cuprates, including Hg1201, we use a tight-binding model to fit their Fermi surfaces. We find a positive correlation between the $T_{c,\mathrm{max}}$ and $t'/t$, consistent with theoretical predictions. 
W.S. Lee, T. Yoshida, W. Meevasana, K.M. Shen, D.H. Lu, W.L. Yang,   X.J. Zhou, X. Zhao, G. Yu, Y. Cho, M. Greven, Z. Hussai...