High-energy magnetic excitations from dynamic stripes in LBCO (x=1/8)

TL;DR

This study investigates how high-energy magnetic excitations in LBCO (x=1/8) persist across the stripe order transition, providing evidence for dynamic stripes in the high-temperature disordered phase through inelastic neutron scattering.

Contribution

It demonstrates that high-energy magnetic excitations remain largely unchanged across the stripe order transition, supporting the existence of dynamic stripes in the disordered phase.

Findings

High-energy magnetic excitations are temperature-independent above the stripe transition.

Momentum-broadening occurs at low energies near the transition temperature.

Dynamic susceptibility remains nearly constant with temperature.

Abstract

We use inelastic neutron scattering to study the temperature dependence of magnetic excitations (for energies up to 100 meV) in the cuprate La$_{1.875}$Ba$_{0.125}$CuO$_4$. This compound exhibits stripe order below a temperature of ~50 K; previous measurements have shown that the magnetic excitations of the stripe-ordered phase have an hour-glass-like dispersion, with a saddle point at ~50 meV. Here we compare measurements in the disordered phase taken at 65 and 300 K. At energies on the scale of $k_{\rm B}T$, there is substantial momentum-broadening of the signal, and the low-energy incommensurate features can no longer be resolved at 300 K. In contrast, there is remarkably little change in the scattered signal for energies greater than $k_{\rm B}T$. In fact, the momentum-integrated dynamic susceptibility is almost constant with temperature. We suggest that the continuity of higher-energy magnetic excitations is strong evidence for dynamic stripes in the high-temperature, disordered phase. We reconsider the nature of the magnetic dispersion, and we discuss the correspondences between the thermal evolution of magnetic stripe correlations with other electronic properties of the cuprates.