Disentangling a quantum antiferromagnet with resonant inelastic X-ray scattering

TL;DR

This paper demonstrates how resonant inelastic X-ray scattering can disentangle quantum entanglement in a copper oxide antiferromagnet by selectively breaking spin chains and revealing magnetic excitations.

Contribution

It introduces a novel X-ray technique using copper M$_2$ and M$_3$ resonances as a natural interferometer to study spin entanglement in cuprates.

Findings

First to use X-ray resonances as a 2-slit interferometer for electronic transitions.

Revealed how electronic excitations influence spin-entangled electrons.

Demonstrated suppression of spin entanglement in SrCuO$_2$.

Abstract

Low-dimensional copper oxide lattices naturally manifest electronic states with strong short range quantum entanglement, which are known to lead to remarkable emergent material properties. However the nanometer scale many-body wavefunction is challenging to measure or manipulate in a simple way. In this study, X-ray induced $dd$ electronic transitions are used to suppress spin entanglement across a single lattice site in the spin-1/2 antiferromagnetic chain compound SrCuO$_2$, revealing a class of cuprate magnetic excitations that result from breaking the spin chain. These measurements are the first to employ two closely spaced X-ray resonances of copper (M$_2$ and M$_3$) as a form of natural 2-slit interferometer to distinguish between different types of electronic transition and resolve how they influence the dynamics of nearby spin-entangled electrons.