139^La NMR Charge Order Study of La_(2-x)Sr_xCuO_4

Abstract

Although charge order was discovered in \lndsco over two decades ago, this elusive state has not been as easily observable in \lsco. \cu NMR experiments demonstrated that \lsco did indeed transition into a charge ordering state, but the lack of evidence in other experiments made many physicists doubtful of its presence. With recent advancements in technology, x-ray scattering experiments have finally been able to measure charge order Bragg peaks in \lsco, proving that charge order anomalies seen by \cu NMR was legitimate. More recent \cu NMR showed that a broad wing-like signal emerges when charge order sets in in \lscoeleven with a much faster relaxation rate than the normal signal. In this thesis, we attempt to revisit the charge ordered state of \lsco by measuring \la NMR on single crystals of x~=~0.13, 0.115 and 0.10. By splitting the relaxation rate into two components, we were able to determine the temperature at which a fast component emerges, corresponding to the same temperature recorded by \cu NMR and x-ray scattering for the same \lscoeleven crystal. Using this method, we measured \la NMR lineshapes and spin-lattice relaxation rates and mapped out the charge order dome of the phase diagram of \lsco.