Multiple bosonic mode coupling in the charge dynamics of the electron-doped superconductor (Pr$_{2-x}$Ce$_x$)CuO$_4$

TL;DR

This study uses optical spectroscopy and advanced analysis to reveal that charge carriers in the electron-doped superconductor PCCO couple to two bosonic modes with distinct temperature-dependent behaviors, shedding light on the pairing mechanism.

Contribution

It introduces a combined maximum entropy and Eliashberg analysis to identify and characterize bosonic modes coupling to charge carriers in PCCO, highlighting differences from hole-doped superconductors.

Findings

Charge carriers couple to modes at ~10 meV and ~45 meV.

The low-energy mode disappears above T_c.

The high-energy mode shifts with temperature and becomes less prominent.

Abstract

We analyze optical spectroscopy data of the electron-doped superconductor (Pr$_{2-x}$Ce$_x$)CuO$_4$ (PCCO) to investigate the coupling of the charge carriers to bosonic modes. The method of analysis is the inversion of the optical scattering rate $\tau^{-1}_{\rm op}(\omega,T)$ at different temperatures $T$ by means of maximum entropy technique combined with Eliashberg theory. We find that in the superconducting state the charge carriers couple to two dominant modes one at $\sim 10 $meV and a second one at $\sim 45 $meV. The low energy mode shows a strong temperature dependence and disappears at or slightly above the critical temperature $T_c$. The high energy mode exists above $T_c$ and moves towards higher energies with increasing temperatures. It also becomes less prominent at temperatures $> 100 $K above which it evolves into a typical spin-fluctuation background. In contrast to the hole-doped High-$T_c$ superconductors PCCO proves to be a superconductor close to the dirty limit.