Doping dependence of the magnetic excitations in La$_{2-x}$Sr$_x$CuO$_4$

TL;DR

This study investigates how magnetic excitations in La$_{2-x}$Sr$_x$CuO$_4$ evolve with doping, revealing systematic softening and broadening, and discusses implications for high-temperature superconductivity.

Contribution

It provides detailed doping-dependent measurements of magnetic excitations along the nodal direction in La$_{2-x}$Sr$_x$CuO$_4$, highlighting their evolution and potential role in superconductivity.

Findings

Magnetic excitations soften and broaden with doping

High energy magnetic excitations persist even in overdoped regime

Low energy excitations' role in pairing remains ambiguous

Abstract

The magnetic correlations within the cuprates have undergone intense scrutiny as part of efforts to understand high temperature superconductivity. We explore the evolution of the magnetic correlations along the nodal direction of the Brillouin zone in La2-xSrxCuO4, spanning the doping phase diagram from the anti-ferromagnetic Mott insulator at x = 0 to the metallic phase at x = 0.26. Magnetic excitations along this direction are found to be systematically softened and broadened with doping, at a higher rate than the excitations along the anti-nodal direction. This phenomenology is discussed in terms of the nature of the magnetism in the doped cuprates. Survival of the high energy magnetic excitations, even in the overdoped regime, indicates that these excitations are marginal to pairing, while the influence of the low energy excitations remains ambiguous.