Detection of a two-phonon mode in a cuprate superconductor via polarimetric RIXS

Abstract

Recent improvements in the energy resolution of resonant inelastic x-ray scattering experiments (RIXS) at the Cu-L${}_3$ edge have enabled the study of lattice, spin, and charge excitations. Here, we report on the detection of a low intensity signal at 140meV, twice the energy of the bond-stretching (BS) phonon mode, in the cuprate superconductor ${\text{Bi}}_2{\text{Sr}}_2\text{Ca}{\text{Cu}}_2{\text{O}}_{8+x}$ (Bi-2212). Ultra-high resolution polarimetric RIXS measurements allow us to resolve the outgoing polarization of the signal and identify this feature as a two-phonon excitation. Further, we study the connection between the two-phonon mode and the BS one-phonon mode by constructing a joint density of states toy model that reproduces the key features of the data.

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Cited by in corpus (2)

• Dynamic charge order from strong correlations in the cuprates
• The influence of phonon symmetry and electronic structure on the electron-phonon coupling momentum dependence in cuprates