Phonon Raman scattering in ( La 1 − x Sr x ) 2 CuO 4 single crystals

摘要: Anomalous Raman spectra were observed in (${\mathrm{La}}_{1\mathrm{\ensuremath{-}}\mathrm{x}}$${\mathrm{Sr}}_{\mathrm{x}}$${)}_{2}$${\mathrm{CuO}}_{4}$ single crystals for the light polarized parallel to layer. The number of peaks are much larger than expected from group-theoretical analysis, supposely due strong phonon-magnon and phonon-free carrier interactions. With increasing x, two-phonon decrease simultaneously with two-magnon peaks; this turn is related correlation length antiferromagnetic spin order. Two-phonon scattering composed a combination two layer-breathing modes layer-quadratic modes, that have electron-phonon interaction. A soft mode orthorhombic-tetragonal phase transition was found incident perpendicular layer, its energy higher by neutron scattering. present indicates symmetry crystal xg0.01 lower orthorhombic.