Von Neumann Entropy Spectra and Entangled Excitations in Spin-Orbital Models

TL;DR

This paper investigates low-energy excitations in one-dimensional spin-orbital models, revealing strongly entangled bound states through von Neumann entropy spectra, and proposes experimental detection via resonant inelastic x-ray scattering.

Contribution

It introduces the von Neumann entropy spectral function to identify entangled spin-orbital bound states and characterizes their universal entanglement scaling.

Findings

Identification of strongly entangled spin-orbital bound states

Universal logarithmic scaling of von Neumann entropy for bound states

Proposal for experimental detection using resonant inelastic x-ray scattering

Abstract

We consider the low-energy excitations of one-dimensional spin-orbital models which consist of spin waves, orbital waves, and joint spin-orbital excitations. Among the latter we identify strongly entangled spin-orbital bound states which appear as peaks in the von Neumann entropy (vNE) spectral function introduced in this work. The strong entanglement of bound states is manifested by a universal logarithmic scaling of the vNE with system size, while the vNE of other spin-orbital excitations saturates. We suggest that spin-orbital entanglement can be experimentally explored by the measurement of the dynamical spin-orbital correlations using resonant inelastic x-ray scattering, where strong spin-orbit coupling associated with the core hole plays a role.