The Persistence of High-Frequency Spin Fluctuations in Overdoped La$_{2-x}$Sr$_{x}$CuO$_{4}$ ($x$=0.22)

TL;DR

This study reveals persistent high-frequency magnetic excitations in overdoped La$_{2-x}$Sr$_{x}$CuO$_{4}$, indicating enduring antiferromagnetic interactions despite doping-induced suppression of low-energy magnetic responses.

Contribution

It provides detailed inelastic neutron scattering data showing high-energy magnetic responses in overdoped cuprates, highlighting the persistence of magnetic interactions beyond optimal doping.

Findings

Suppression of low-energy magnetic response in overdoped La$_{2-x}$Sr$_{x}$CuO$_{4}$

Presence of strong high-energy magnetic excitations at E >= 80 meV

Magnetic response remains peaked at incommensurate wavevectors across energies

Abstract

We report a detailed inelastic neutron scattering study of the collective magnetic excitations of overdoped superconducting La1.78Sr0.22CuO4 for the energy range 0-160 meV. Our measurements show that overdoping suppresses the strong response present for optimally doped La2-xSrxCuO4 which is peaked near 50 meV. The remaining response is peaked at incommensurate wavevectors for all energies investigated. We observe a strong high-frequency magnetic response for E >= 80 meV suggesting that significant antiferromagnetic exchange couplings persist well into the overdoped part of the cuprate phase diagram.