Quasiparticle dynamics and in-plane anisotropy in YBa2Cu3Oy near the onset of superconductivity -: art. no. 014518

We report on an infrared study of carrier dynamics within the CuO2 planes in heavily underdoped detwinned single crystals of YBa2Cu3Oy. In an effort to reveal the electronic structure near the onset of superconductivity, we investigate the strong anisotropy of the electromagnetic response due to an enhancement of the scattering rate along the a axis. We propose that the origin of this anisotropy is related to a modulation of the electron density within the CuO2 planes.