Quasiparticlelike Peaks, Kinks, and Electron-Phonon Coupling at the(π,0)Regions in the CMR OxideLa2−2x

Abstract

Using angle-resolved photoemission, we have observed sharp quasiparticlelike peaks in the prototypical layered manganite La(2-2x)Sr(1+2x)Mn(2)O(7) (x=0.36,0.38). We focus on the (pi,0) regions of k space and study their electronic scattering rates and dispersion kinks, uncovering bilayer-split bands, the critical energy scales, momentum scales, and strengths of the interactions that renormalize the electrons. To identify these bosons, we measured phonon dispersions in the energy range of the kink by inelastic neutron scattering, finding a good match in both energy and momentum to the oxygen bond-stretching phonons.

A local metallic state in globally insulating La1.24Sr1.76Mn2O7 well above the metal–insulator transition

“…High-quality low-energy electron diffraction pictures without any evidence of surface reconstruction are obtained from these surfaces. The doping level at the surfaces, as obtained from the Fermi surface LETTERS volume, also seems to be correct for these samples-for example the d x 2 −y 2 bonding-band Fermi surface nesting vector of 0.27 × (2π/a) for the x = 0.38 samples used in this study 4 exactly matches that obtained from neutron scattering measurements 21 . The nesting vector of 0.4 samples is slightly larger, at 0.3 × (2π/a) (ref.…”

“…As discussed in ref. 4, the x = 0.36, 0.38 compounds studied here do not contain the lowenergy pseudogap of the x = 0.4 samples [5][6][7][8] (see the Methods section for more details on this, the possible issue of surface sensitivity of ARPES and of possible intergrowths at the surface). The much larger metallic spectral weight of these nonpseudogapped compounds also allows us to study the electronic behaviour in greater detail.…”

“…We are able to get clean data by isolating the various bilayer-split bands using different photon energies, as described in ref. 4. In particular, in this paper we show only data from the antibonding bilayer-split band, which has Fermi crossings at k x = ±0.17π/a, k y = 0.9π/a, corresponding to the solid Fermi surface of the inset of Fig.…”

“…1a, the colossal magnetoresistive (CMR) oxide La 2−2x Sr 1+2x Mn 2 O 7 (x = 0.36,0.38) shows a metal-insulator transition at a T C just below 130 K, at which point the system also switches from being a ferromagnet (low temperature T) to a paramagnet (high T) 3 . We carried out angle-resolved photoemission spectroscopy (ARPES) experiments on cleaved single crystals of these materials, with an experimental arrangement as described elsewhere 4 . ARPES is an ideal experimental probe of the electronic structure because it gives the momentum-resolved single-particle excitation spectrum.…”

Empirical relationship between x-ray photoemission spectra and electrical conductivity in a colossal magnetoresistive manganite La1−xSrxMnO3

“…16 Instead, only a few angle-resolved studies on layered manganites have succeeded in observing an extremely small quasiparticle peak in very limited k-space areas. 17,18 Nevertheless, the temperature dependence of the near-E F spectral weight over hundreds meV was found to follow that of the Drude weight or electrical conductivity, 19 reproducing the agreement between the temperature dependence of the quasiparticle peak weight (with the width of ∼50 meV) and that of the electrical conductivity. 20 Again, there have been no x-dependent studies on this issue so far.…”