Raman Studies of Anisotropic Magnetic Excitations in Fluctuating Nematic Striped La2−x Sr x CuO4 and the Comparison to Uniform Nd2−x Ce x CuO4

Abstract

The mechanism of the high temperature hole-doped superconductivity was investigated by Raman scattering. The Raman selection rule is unique, so that anisotropic magnetic excitations in a fluctuating spin-charge stripe can be detected as if it is static. We use different Raman selection rules for two kinds of magnetic Raman scattering processes, two-magnon scattering and high-energy electronic scattering. In order to confirm the stripe effect, the Raman spectra of striped La2−x Sr x CuO4 (LSCO) and nonstriped Nd2−x Ce x CuO4 (NCCO) were compared. The main results in LSCO are (1) magnetic excitations are presented by individual energy dispersions for the k∥ stripe and the k⊥ stripe, (2) the charge transfer is allowed only in the direction perpendicular to the stripe. The direction is the same as the Burgers vector of an edge dislocation. Hence, we assume that a charge moves together with the edge dislocation of the charge stripe. The superconducting coherence length is close to the intercharge stripe distance at x<0.2. Therefore, we propose a model that superconducting pairs are formed in the edge dislocations. The binding energy is related to the stripe formation energy.