Effects of charge inhomogeneities on elementary excitations inLa2−xSrxCuO4

Abstract

Purely local experimental probes of many copper oxide superconductors show that their electronic states are inhomogeneous in real space. For example, scanning tunneling spectroscopic (STS) imaging shows strong variations in real space, and according to nuclear quadrupole resonance (NQR) studies the charge distribution in the bulk varies on the nanoscale. However, the analysis of the experimental results utilizing spatially-averaged probes often ignores this fact. We have performed a detailed investigation of the doping-dependence of the energy and line width and position of the zone-boundary Cu-O bond-stretching vibration in La2−xSrxCuO4 by inelastic neutron scattering. Both our new results as well as previously reported angle-dependent momentum widths of the electronic spectral function detected by angle-resolved photoemission can be reproduced by including the same distribution of local environments extracted from the NQR analysis.

Phonon anomalies and dynamic stripes

“…[50] These experiments and related calculations are extensively covered in the previous review by L. Pintschovius. [10] A recent investigation of Park et al [51] also revealed that the linewidth of the zone boundary bond-stretching phonon (around q=(0.5,0,0)) broadens strongly when the doping, x, is reduced and then narrows abruptly at x=0. They explained this effect in light of NQR/NMR results showing that the doped carrier concentration in the Cu-O planes is inhomogeneous, and since the zone boundary phonon frequency depends on doping, the experimental lineshape broadens.…”

“…Note that the enhancement of the linewidth at x=0.07 near the zone boundary compared with the higher dopings is unrelated to the anomaly at h=0.3 and can be explained by the inhomogeneous doping effect discussed in sec. 4.1 and[51].…”

Evidence for a charge collective mode associated with superconductivity in copper oxides from neutron and x-ray scattering measurements of La2−xSrxCuOPark1, Fukuda2, Hamann3 et al. 2014Phys. Rev. BSelf Cite450362View full textAdd to dashboardCite

“…It was shown in Ref. 20 that this effect originates from inhomogeneous doping combined with doping-induced phonon softening at Sr concentrations below optimal doping. Since the dopingdependence of the phonon frequency increases towards the zone boundary, the width of the measured phonon spectrum increases smoothly towards the zone boundary as well.…”

Relaxation timescales and electron-phonon coupling in optically-pumped YBa$_2$Cu$_3$O$_{6+x}$ revealed by time-resolved Raman scattering

“…However phonon-phonon coupling (anharmonicity) also broadens the phonon peaks and electron-electron interactions can broaden the electronic quasiparticles. Disorder can further increase the linewidths [13], so extracting electron-phonon coupling strength from the linewidths of quasiparticle peaks is challenging.…”