Spin excitations coupled with lattice and charge dynamics in LaSrCuO

Ikeuchi, Kazuhiko*; Wakimoto, Shuichi  ; Fujita, Masaki*; Fukuda, Tatsuo  ; Kajimoto, Ryoichi  ; Arai, Masatoshi*

Spin excitations of layered copper oxide show various characteristic features, depending on the carrier concentration. In this paper, we conducted inelastic neutron-scattering measurements on LaSrCuO (LSCO) with = 0, 0.075, 0.18, and 0.30 and LaSrNiO (LSNO) with 1/3 to clarify the origin of the intensity enhancement in the excitation spectrum of LSCO at the energy () of 16-19 meV [Phys. Rev. B , 224404 (2015), , 094416 (2016)]. We confirmed the presence of a peak structure in the dependence of the local spin susceptibility of superconducting (SC) LSCO with a peak energy of 16-19 meV where the spin excitations intersect optical phonon branches. A comparable peak structure is not observed in the insulating LaCuO, LSNO, and heavily overdoped LSCO with = 0.30. A dome-shaped dependence of the integrated intensity around the peak energies is revealed for the SC phase by summarizing the present and previously reported results. Furthermore, our phonon calculation on LCO shows the existence of two optical branches at 19 meV that could stabilize stripe alignment of carriers due to out-of-plane vibrations of Cu or O of the CuO planes. These results indicate the interplay among spin, charge, and lattice dynamics and suggest that the intensity enhancement is associated with their composite excitations.