Spin excitations in layered antiferromagnetic metals and superconductors

TL;DR

This paper investigates spin excitations in layered antiferromagnetic metals and superconductors, analyzing how doping and Fermi surface topology influence the spectrum, with implications for neutron scattering and pairing mechanisms.

Contribution

It provides a detailed analysis of spin excitation spectra in SDW and coexistence states, highlighting the role of low-energy particle-hole excitations and their evolution with doping.

Findings

Identification of spin-wave and particle-hole excitations in different doping regimes

Low-energy particle-hole excitations are significant in partially gapped states

Implications for neutron scattering experiments and superconducting pairing theories

Abstract

The proximity of antiferromagnetic order in high-temperature superconducting materials is considered a possible clue to the electronic excitations which form superconducting pairs. Here we study the transverse and longitudinal spin excitation spectrum in a one-band model in the pure spin density wave (SDW) state and in the coexistence state of SDW and the superconductivity. We start from a Stoner insulator and study the evolution of the spectrum with doping, including distinct situations with only hole pockets, with only electron pockets and with pockets of both types. In addition to the usual spin-wave modes, in the partially gapped cases we find significant weight of low-energy particle-hole excitations. We discuss the implications of our findings for neutron scattering experiments and for theories of Cooper-pairing in the metallic SDW state.