Doping Dependence of Low-energy Spin Fluctuations in Electron-Doped Cuprates Pr$_{1-x}$LaCe$_x$CuO$_4$

TL;DR

This study investigates how low-energy spin fluctuations in electron-doped Pr$_{1-x}$LaCe$_x$CuO$_4$ evolve across different doping levels, revealing their close connection to the emergence and disappearance of superconductivity.

Contribution

It provides a comprehensive analysis of doping-dependent spin fluctuations in Pr$_{1-x}$LaCe$_x$CuO$_4$, highlighting their role in superconductivity.

Findings

Spin fluctuations are centered at ($,$) for all doping levels.

Characteristics of excitations change rapidly with doping, especially entering the superconducting phase.

Spin stiffness decreases with doping and vanishes at the end of superconductivity.

Abstract

The low-energy spin fluctuations in the electron-doped Pr$_{1-x}$LaCe$_{x}$CuO$_{4}$ have been investigated over a wide concentration range of 0.07$\leqslant$ $x$ $\leqslant$0.18 that spans from the antiferromagnetic and non-superconducting phase to the superconducting and paramagnetic phase. For all concentrations considered, the low energy excitations exhibit commensurate peaks centered at the ($\pi$, $\pi$) position. Our data show that the characteristics of the excitations, such as the relaxation rate and the overall spectral weight, change rapidly when the system enters the superconducting phase. The spin stiffness also decreases with increasing $x$ in the superconducting phase and is extrapolated to zero at $x$ = 0.21 when the superconductivity disappears. These indicate a close relation between the spin fluctuations and the superconductivity in the electron-doped system.