BCS $d$-wave behavior in the THz electrodynamic response of electron-doped cuprate superconductors

TL;DR

This study uses THz spectroscopy to analyze the electrodynamic response of electron-doped cuprate superconductors, revealing BCS $d$-wave characteristics consistent with a disordered superconductor model.

Contribution

It provides experimental evidence supporting a disordered BCS $d$-wave model for superconductivity in electron-doped cuprates through detailed THz response measurements.

Findings

Temperature dependence follows $n_s \,\propto\, 1-(T/T_c)^2$

Magnetic field dependence follows a $\,\sqrt{B}$ form

Supports $d$-wave symmetry in electron-doped cuprates

Abstract

Although cuprate superconductors have been intensively studied for the past decades, there is no consensus regarding the microscopic origin of their superconductivity. In this work, we measure the low-energy electrodynamic response of slightly underdoped and overdoped La$_{2-x}$Ce$_x$CuO$_4$ thin films using time-domain terahertz (THz) spectroscopy to determine the temperature and field dependence of the superfluid spectral weight. We show that the temperature dependence obeys the relation \textit{n$_s$} $\propto$ $1-(T/T_c)^2$, typical for dirty limit BCS-like $d$-wave superconductors. Furthermore, the magnetic field dependence was found to follow a sublinear $\sqrt{B}$ form, which supports predictions based on a $d$-wave symmetry for the superconducting gap. These observations imply that the superconducting order in these electron-doped cuprates can be well described in terms of a disordered BCS $d$-wave formalism.