La <sub> 2 </ Sub> Charge Ordering Of Cuo <sub> 4 </ Sub> Superconductors And Its Ultrasonic Attenuation Characteristics Of Study

There is a growing evidence that charges and spins are self-organized in CuO₂ planes in a peculiar striped manner in high temperature cuprates, where the doped holes are arranged in one-dimensional (1D) lines, "charge stripes" that separate the antiferromagnetic domains. What a role of charge stripe order plays in high temperature superconductivity and normal state properties has become one of the most interesting hot topics in condensed matter physics.In this dissertation, the transport properties, the interaction between charge stripes and structure distortion, the effect of magnetic field on the charge stripe order and the relationship between charge stripe order and superconductivity in La-based cuprates were studied systematically. In addition, the Raman spectra of Na_xCoO₂ were also studied.The progresses in the studies on the charge stripe phase in high temperature superconductors were reviewed in chapter one. The main contents include: the picture of stripe phase, the relationship between charge stripes and crystal lattice, experimental evidences for the 1D transport of the charges in cuprates, and so on. The relationship between superconductivity and charge stripe order is analyzed and some open questions are discussed at the end of the chapter.In chapter two, the structure, transport properties, ultrasonic sound velocity and attenuation of La_1.88-yNd_ySr_0.12CuO₄ were studied. The X-ray diffraction (XRD) patterns at room temperature suggest that Nd doping favors the tilting of CuO₆ octahedra. Temperature dependence of XRD pattern of La_1.48Nd_0.4Sr_0.12CuO₄ shows a structure phase transition from low-temperature orthorhombic (LTO) to low-temperature tetragonal (LTT) around 70 K. It was found that the resistivity behavior of the samples can be well described by a 1D transport model in LTO phase and show a log(1/T) behavior in LTT phase. The anomaly stiffening of ultrasonic sound velocity and the attenuation peak around LTO-LTT structure phase transition temperature suggest the formation of static charge stripes. The interaction between dynamic charge stripes and structure distortion was identified by a...