Raman scattering investigation of the electron-phonon coupling in superconducting Nd(O,F)BiS$_2$

TL;DR

This study uses polarized Raman scattering to investigate electron-phonon interactions in the superconductor Nd(O,F)BiS$_2$, revealing phonon modes and their coupling contributions, supporting phonon-mediated superconductivity.

Contribution

First-principles calculations combined with Raman measurements identify specific phonon modes and their electron-phonon coupling, suggesting phonon-mediated pairing in Nd(O,F)BiS$_2$.

Findings

Observation of 2 Raman active modes consistent with calculations.

Identification of a Fano line shape indicating electron-phonon coupling.

Estimated contribution of a phonon mode to the electron-phonon coupling constant.

Abstract

We have performed polarized Raman scattering measurements on the newly discovered superconductor Nd(O,F)BiS$_2$ ($T_c = 4$ K). We observe 2 Raman active modes, with frequencies in accordance with first-principles calculations. One A$_{1g}$ phonon mode at 112.4 cm$^{-1}$ exhibits a Fano line shape due to electron-phonon coupling. We find a resonance for this mode at 2.45 eV excitation energy. We estimate a 0.68 contribution of this mode to the electron-phonon coupling constant $\lambda$. Our Raman results suggest that the BiS$_2$-based superconductors are possibly phonon-mediated BCS superconductors.