Evolution of low-energy spin dynamics in the electron-doped high-transition-temperature superconductorPr0.88LaCe0.12CuO4−δ

Abstract

We use inelastic neutron scattering to explore the evolution of the low energy spin dynamics in the electrondoped cuprate Pr 0.88 LaCe 0.12 CuO 4−␦ ͑PLCCO͒ as the system is tuned from its nonsuperconducting, as-grown antiferromagnetic ͑AF͒ state into an optimally doped superconductor ͑T c Ϸ 24 K͒ 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.

Electron-spin excitation coupling in an electron-doped copper oxide superconductor

“…Spatial mapping of the modes shows nanoscale regions of coexisting AF and superconducting order in the lower T c samples. Since the annealing process is not expected to change lattice (phonon) properties 2,13,14,18 , these results demonstrate that antiferromagnetism and superconductivity compete locally and coexist spatially on nanometer length scales, and the dominant electron-boson coupling at low energies originates from the electron-spin excitations 17 rather than electron-phonon interactions 19 .There is experimental and theoretical evidence suggesting that antiferromagnetism is a competing phase to superconductivity in electron and hole doped copper oxides [1][2][3][4][5] . In samples where antiferromagnetism and superconductivity coexist, the spatial configuration of these two phases can provide important information on the strength of electron correlations 3,5 and the extent to which antiferromagnetism contributes to electron pairing [1][2][3][4][5] .…”

“…Spatial mapping of the modes shows nanoscale regions of coexisting AF and superconducting order in the lower T c samples. Since the annealing process is not expected to change lattice (phonon) properties 2,13,14,18 , these results demonstrate that antiferromagnetism and superconductivity compete locally and coexist spatially on nanometer length scales, and the dominant electron-boson coupling at low energies originates from the electron-spin excitations 17 rather than electron-phonon interactions 19 .…”

“…High-temperature (high-T c ) superconductivity in the copper oxides arises from electron or hole doping of their antiferromagnetic (AF) insulating parent compounds 1,2 . The evolution of the AF phase with doping and its spatial coexistence with superconductivity are governed by the nature of charge and spin correlations and provide clues to the mechanism of high-T c superconductivity 3,4 .…”

“…Electron correlation in hole-and electrondoped materials can be quite different 5 . While doped electrons reside in the Cu 3d orbitals with correlations involving primarily d-electrons 2 , doped holes form Zhang-Rice singlets moving in the background of Cu spins 1 and are subject to stronger correlations [1][2][3][4][5][6][7] . In electron-doped copper oxides, there are bulk signatures of coexisting AF and superconducting phases [8][9][10][11][12] .…”

“…There is experimental and theoretical evidence suggesting that antiferromagnetism is a competing phase to superconductivity in electron and hole doped copper oxides [1][2][3][4][5] . In samples where antiferromagnetism and superconductivity coexist, the spatial configuration of these two phases can provide important information on the strength of electron correlations 3,5 and the extent to which antiferromagnetism contributes to electron pairing [1][2][3][4][5] .…”