Angle-resolved photoemission spectroscopy of electron-doped cuprate superconductors: Isotropic electron-phonon coupling

TL;DR

This study uses high-resolution ARPES to investigate electron-phonon interactions in electron-doped cuprate superconductors, revealing isotropic coupling to phonons at specific energies, regardless of doping or rare earth element.

Contribution

It demonstrates that electron-phonon coupling in electron-doped cuprates is isotropic and consistent across different doping levels, contrasting with hole-doped cuprates.

Findings

Step-like features in self energy indicate electron-bosonic mode coupling.

Coupling energies are at 50 and 70 meV, linked to phonon modes.

Electron-phonon coupling constant lambda is doping and momentum independent.

Abstract

We have performed high resolution angle resolved photoemission (ARPES) studies on electron doped cuprate superconductors Sm2-xCexCuO4 (x=0.10, 0.15, 0.18), Nd2-xCexCuO4 (x=0.15) and Eu2-xCexCuO4 (x=0.15). Imaginary parts of the electron removal self energy show step-like features due to an electron-bosonic mode coupling. The step-like feature is seen along both nodal and anti-nodal directions but at energies of 50 and 70 meV, respectively, independent of the doping and rare earth element. Such energy scales can be understood as being due to preferential coupling to half- and full-breathing mode phonons, revealing the phononic origin of the kink structures. Estimated electron-phonon coupling constant lambda from the self energy is roughly independent of the doping and momentum. The isotropic nature of lambda is discussed in comparison with the hole doped case where a strong anisotropy exists.