Parametrization of optical conductivity of the prototypic high-Tc cuprate La2−xSrxCuO4

With the aim to propose a description as general as possible of ‘non-metallic’ conducting materials, including the class of high-Tc cuprate superconductors, we test a model based on the generalization of the Lyddane–Sachs–Teller relationship on the prototype of the class. This is also an extension of the conventional Drude model. It is shown to fit closely with the infrared–visible–near ultraviolet reflection spectra of La2−xSrxCuO4 for all x varying from 0 to 0.34. Polaron formation is highly suggested for low x and the model makes it possible to discriminate the trapped polarons from the mobile species. The two- to three-dimensional change of regime is accompanied by a diffusive non-Drude to conventional pseudo-Drude behavior of the mobile charge carriers.