Doping-induced modifications in the infrared-active phonons of La2-xSrxCuO4

The absorption spectra of polycrystalline La2-xSrxCuO4 have been studied in the far-infrared for x = 0, 0.023, 0.040, 0.051, 0.106 and for 20 less tha n or equal to T less than or equal to 300 K. The effects of doping and temp erature on the a-b plane Cu-O stretching phonon around 680 cm(-1) are consi dered. This in-plane phonon is increasingly shielded by charges injected by doping and is strongly affected by a Fano interaction with an electronic c ontinuum. Basing on similarities with the spectra of Nd2-xCexCuO4 and on th e evolution of the Fano effect with x and T, the continuum is attributed to a polaronic band. (C) 2001 Elsevier Science B.V. All rights reserved.