Extended Data Fig. 1: RIXS phonon softening in LaNiO2 at 20 K and fit of the spectra.
From: A broken translational symmetry state in an infinite-layer nickelate
a, Representative RIXS spectrum of LaNiO2 (black circles) at q// = (0.4, 0) r.l.u. and corresponding fit (red solid line). The fit function includes a Gaussian for the elastic line (orange), anti-symmetrized Lorentzian for phonon (blue) and magnon (green) and a constant background (thin black line). The fit function is convolved with a Gaussian with FWHM = 36 meV. b, Phonon dispersion clearly showing the softening of the RIXS phonon. The phonon dispersion is also shown in Fig. 1a of the main text. c, Raw RIXS spectra of LaNiO2 (black circles) with fit superimposed (red lines). The data shown here were taken using σ incident photon polarization to optimize the RIXS phonon signal.
