We present a comprehensive study of the phonon dispersion in an underdoped, superconducting Ca2−xCuO2Cl2 crystal. We interpret the results using lattice dynamical calculations based on a shell model, and we compare the results, to other hole-doped cuprates, in particular to the ones isomorphic to La2−xSrxCuO4 (LSCO). We found that an anomalous dip in the Cu-O bond stretching dispersion develops in oxychlorides with a simultaneous marked broadening of the mode. The broadening is maximum at ≈(π/(2a)00) that corresponds to the charge-modulations propagation vector. Our analysis also suggests that screening effects in calculations may cause an apparent cosine-shaped bending of the Cu-O bond-stretching dispersion along both the (q 0 0) and (qq 0) directions, that is not observed on the data close to optimal doping. This observation suggests that the discrepancy between experimental data and \textit{ab-initio} calculations on this mode originates from an overestimation of the doping effects on the mode.
@article{arxiv.1305.6719,
title = {Phonon anomalies and lattice dynamics in superconducting oxychlorides Ca$_{2-x}$CuO$_2$Cl},
author = {Matteo D'Astuto and Ikuya Yamada and Paola Giura and Lorenzo Paulatto and Andrea Gauzzi and Moritz Hoesch and Michael Krisch and Masaki Azuma and Mikio Takano},
journal= {arXiv preprint arXiv:1305.6719},
year = {2013}
}