Doping dependence of the gap anisotropy in LCCO studied by millimeter-wave spectroscopy

TL;DR

This study investigates how electron doping affects the gap anisotropy in La2-xCexCuO4 by measuring the penetration depth across different doping levels and temperatures, revealing a transition from quadratic to exponential behavior.

Contribution

It provides new insights into the doping-dependent evolution of the superconducting gap anisotropy in electron-doped cuprates using millimeter-wave spectroscopy.

Findings

Quadratic temperature dependence in underdoped samples

Near-exponential increase at optimal doping

Doping-induced changes in gap anisotropy or symmetry

Abstract

We measure the penetration depth of optimally doped and underdoped La2-xCexCuO4 in the millimeter frequency domain (4 - 7 cm-1) and for temperatures 2 K < T < 300 K. The penetration depth as function of temperature reveals significant changes on electron doping. It shows quadratic temperature dependence in underdoped samples, but increases almost exponentially at optimal doping. Significant changes in the gap anisotropy (or even in the gap symmetry) may account for this transition.