Spin Waves in Striped Phases

TL;DR

This paper investigates the spin wave spectra in stripe phases of antiferromagnetic materials, revealing qualitative differences between bond-centered and site-centered stripes and their implications for neutron scattering responses.

Contribution

It provides a comparative analysis of spin wave spectra for bond-centered and site-centered stripe configurations using a parametrized Heisenberg model, highlighting their distinct neutron scattering signatures.

Findings

Bond-centered stripes show more elastic peaks than site-centered ones.

Bond-centered stripes produce more spin wave bands and isotropic low-energy cones.

Diagonal stripes are more likely to exhibit crossing spin wave modes linked to the resonance peak.

Abstract

In many antiferromagnetic, quasi-two-dimensional materials, doping with holes leads to "stripe" phases, in which the holes congregate along antiphase domain walls in the otherwise antiferromagnetic texture. Using a suitably parametrized two-dimensional Heisenberg model on a square lattice, we study the spin wave spectra of well-ordered spin stripes, comparing bond-centered antiphase domain walls to site-centered antiphase domain walls for a range of spacings between the stripes and for stripes both aligned with the lattice ("vertical") and oriented along the diagonals of the lattice ("diagonal"). Our results establish that there are qualitative differences between the expected neutron scattering responses for the bond-centered and site-centered cases. In particular, bond-centered stripes of odd spacing generically exhibit more elastic peaks than their site-centered counterparts. For inelastic scattering, we find that bond-centered stripes produce more spin wave bands than site-centered stripes of the same spacing and that bond-centered stripes produce rather isotropic low energy spin wave cones for a large range of parameters, despite local microscopic anisotropy. We find that extra scattering intensity due to the crossing of spin wave modes (which may be linked to the "resonance peak" in the cuprates) is more likely for diagonal stripes, whether site- or bond-centered, whereas spin wave bands generically repel, rather than cross, when stripes are vertical.