Effect of electron-phonon coupling in the ARPES spectra of the tri-layer cuprate Bi2Sr2Ca2Cu3O10+δ
Angle-resolved photoemission spectroscopy using tunable low energy photons allows us to study the quasi-particle (QP) dispersions of the inner and outer CuO2 planes (IP and OP) separately in the tri-layer cuprate Bi2Sr2Ca2Cu3O10+δ (Bi2223). The kink energy of the OP band is ~ 70 meV, as observed in various high-Tc cuprates, while that of the IP band is as large as ~ 100 meV in the superconducting (SC) state. This large kink energy is attributed to the ~35 meV buckling mode plus the large (~ 60 meV) SC gap of IP. The IP band also shows a weak kink feature at ~ 70 meV in the SC state. The latter feature can be explained either by the 70 meV half-breathing mode or by the ~ 35 meV buckling-phonon mode plus the ~ 40 meV SC gap of OP if interlayer scattering of QP is involved.