Magnetic Excitations of Stripes Near a Quantum Critical Point

TL;DR

This paper investigates the magnetic excitations in stripe-ordered systems near a quantum critical point, revealing energy-dependent features in the spin structure factor that resemble experimental neutron scattering data on cuprates.

Contribution

It provides a semiclassical calculation of the dynamical spin structure factor for weakly coupled stripes, connecting classical and quantum behaviors near a quantum critical point.

Findings

Low energy spin wave cone peaks are strongly peaked on inner branches.

At higher energy, a saddlepoint appears followed by a rotated square-shaped continuum.

Results resemble high energy neutron scattering data on cuprates.

Abstract

We calculate the dynamical spin structure factor of spin waves for weakly coupled stripes. At low energy, the spin wave cone intensity is strongly peaked on the inner branches. As energy is increased, there is a saddlepoint followed by a square-shaped continuum rotated 45 degree from the low energy peaks. This is reminiscent of recent high energy neutron scattering data on the cuprates. The similarity at high energy between this semiclassical treatment and quantum fluctuations in spin ladders may be attributed to the proximity of a quantum critical point with a small critical exponent $\eta$.