Interplay between the pseudogap and superconductivity in HgBa$_2$CuO$_4$   single crystals
  We report a doping dependant Electronic Raman Scattering (ERS) study of HgBa$_2$CuO$_{4+\delta}$ (Hg-1201) single crystals. We investigate the dynamics of the antinodal and nodal quasiparticles. We show that the dynamical response of the antinodal quasiparticles is strongly reduced towards the underdoped regime in both the normal and superconducting states. When probing the nodal quasiparticles, we are able to distinguish between the energy scale of the pseudogap and that of the superconducting gap. A simple model relating the suppression of the dynamical response of the antinodal quasiparticles to fluctuations related to a competing phase is proposed. 
Y. Gallais, A. Sacuto, T. P. Devereaux and D. Colson