Evolution of low-energy spin dynamics in the electron-doped high-transition-temperature superconductor Pr 0.88 LaCe 0.12 CuO 4-δ

We use inelastic neutron scattering to explore the evolution of the low energy spin dynamics in the electron-doped cuprate Pr0.88LaCe0.12CuO4-delta (PLCCO) as the system is tuned from its nonsuperconducting, as-grown antiferromagnetic (AF) state into an optimally doped superconductor (T-c approximate to 24 K) without static AF order. The low-temperature, low-energy response of the spin excitations in underdoped samples is coupled to the presence of the AF phase, whereas the low-energy magnetic response for samples near optimal T-c exhibits spin fluctuations surprisingly insensitive to the sample temperature. This evolution of the low-energy excitations is consistent with the influence of a quantum critical point in the phase diagram of PLCCO associated with the suppression of the static AF order. We carried out scaling analysis of the data and discuss the influence of quantum critical dynamics in the observed excitation spectrum.