Magnetic Response in the Underdoped Cuprates

TL;DR

This paper presents a phenomenological theory explaining the magnetic response in underdoped cuprates, predicting an hourglass-shaped spin response across energy scales consistent with experimental observations.

Contribution

It introduces a doped resonant valence bond model with Fermi surface pockets to semi-quantitatively describe magnetic excitations in underdoped cuprates.

Findings

Predicted hourglass-shaped magnetic response from 0 to 100 meV.

Identified low-energy spin response at specific momentum points.

Described high-energy scattering from (pi,0) to (pi,pi).

Abstract

We examine the dynamical magnetic response of the underdoped cuprates by employing a phenomenological theory of a doped resonant valence bond state where the Fermi surface is truncated into four pockets. This theory predicts a resonant spin response which with increasing energy (0 to 100meV) appears as an hourglass. The very low energy spin response is found at (pi,pi +- delta) and (pi +- delta,pi) and is determined by scattering from the pockets' frontside to the tips of opposite pockets where a van Hove singularity resides. At energies beyond 100 meV, strong scattering is seen from (pi,0) to (pi,pi). This theory thus provides a semi-quantitative description of the spin response seen in both INS and RIXS experiments at all relevant energy scales.