Collective Excitations in High-Temperature Superconductors

TL;DR

This paper investigates low-energy collective excitations in high-temperature superconductors, highlighting the role of spin-density waves and their potential connection to experimental spectral and neutron-scattering observations.

Contribution

It introduces the analysis of spin-density-wave excitations within d-wave superconductors and their relevance to high-Tc superconductor phenomena near the antiferromagnetic phase.

Findings

Spin-density-wave modes can propagate within the superconducting gap.

Long-range Coulomb interactions shift charge and phase modes to plasma energy.

These excitations may explain features observed in spectral-density and neutron-scattering data.

Abstract

Collective, low-energy excitations in quasi-two-dimensional d-wave superconductors are analyzed. While the long-range Coulomb interaction shifts the charge-density-wave and phase modes up to the plasma energy, the spin-density-wave excitation that arises due to a strong local electron-electron repulsion can propagate as a damped collective mode within the superconducting energy gap. It is suggested that these excitations are relevant to high-Tc superconductors, close to the antiferromagnetic phase boundary, and may explain some of the exotic features of the experimentally observed spectral-density and neutron-scattering data.