Non-BCS temperature dependence of energy gap in thin film electron-doped cuprates

TL;DR

This study examines how the energy gap in electron-doped cuprate thin films varies with temperature, revealing deviations from BCS theory especially at lower cerium concentrations and structural instability at high doping levels.

Contribution

It provides new insights into the non-BCS temperature dependence of the energy gap in electron-doped cuprates across different cerium concentrations.

Findings

G(T) deviates from BCS predictions at low cerium levels.

Residual Nernst region affects the energy gap behavior.

Structural instability occurs at maximum cerium doping.

Abstract

We investigate the dependence of the energy gap ($G$) on the temperature ($T$) for the electron-doped high-temperature superconductors. The following compounds, in the form of the thin films, have been taken into consideration: $\rm La_{2-x}Ce_xCuO_{4}$ (LCCO), $\rm Pr_{2-x}Ce_xCuO_{4}$ (PCCO), and $\rm Nd_{2-x}Ce_xCuO_4$ (NCCO). It was found that $G\left(T\right)$ deviates from the BCS prediction more, if a concentration of cerium assumes the lower values. For the lowest concentration (in the case of LCCO and NCCO), the function $G\left(T\right)$ is not quite like the BCS curve, which is connected with the existence of the residual Nernst region. Next, it has been pointed out that the NCCO superconductor becomes structurally unstable for the maximum concentration of cerium, which is leading to the anomalous dependence of the energy gap on the temperature and the induction of the wide Nernst region.