Electron-phonon coupling of Bi2212 cuprate superconductor

Hsiao-Yu Huang^1*, J. Okamoto¹, A. Singh¹, Y.-Y. Chu¹, J.-H. Lee², T. Watanabe³, A. Fujimori⁴, C.-T. Chen¹, D.-J. Huang^1,2

¹National Synchrotron Radiation Research Center, Hsinchu City, Taiwan
²Department of Physics, National Tsing Hua University, Hsinchu City, Taiwan
³Graduate School of Science and Technology, Hirosaki University, Hirosaki, Japan
⁴Department of Physics, University of Tokyo, Tokyo, Japan

* Presenter:Hsiao-Yu Huang, email:huang.hy@nsrrc.org.tw

The coupling between phonons and valence electrons plays a key role in condensed matter physics. For example, the attraction due to the electron–phonon interaction in a conventional superconductor gives rise to a Cooper pair, which is responsible for its superconductivity. Interestingly it has been suggested that interplay of electron-phonon coupling (EPC) and electron correlation collaborate to enhance the d-wave pairing in cuprate superconductors. Recently many experiments show that charge order is ubiquitous in cuprates. The effect of EPC in charge density wave (CDW) modulations and its role in copper-based high-temperature superconductors are still unclear. Here we present the study of O K-edge resonant inelastic X-ray scattering (RIXS) in optimally doped Bi₂Sr₂CaCu₂O_8+δ (Bi2212; T_c ~ 90 K) superconductor. With an energy resolution better than 25 meV, we observed three breathing and buckling phonons and the phonon anomaly aross the CDW wave vector. Our results demonstrate the sensitivity of O K-edge RIXS in electron-phonon coupling of hole doped cuprate superconductors. The effect of electron correlations on EPC in cuprates will be discussed.

Keywords: RIXS, cuprate superconductor, electron-phonon coupling