Orbital current signature using neutron diffraction

TL;DR

This paper reviews how polarized neutron diffraction detects orbital loop currents in various correlated electron materials, highlighting their signatures, experimental evidence, and theoretical descriptions over the past two decades.

Contribution

It introduces an alternative microscopic current-based approach to describe neutron magnetic scattering, complementing the traditional local magnetic moment perspective.

Findings

Orbital loop currents have been observed in high-Tc cuprates, iridates, and kagome vanadates.

Neutron diffraction detects orbital magnetic moments induced by these currents.

A new microscopic current-based description of neutron magnetic cross-section is proposed.

Abstract

We review the hallmarks of orbital loop currents in various correlated electron materials and how they have been evidenced using polarized neutron diffraction. Over the last 20 years, loop current signatures have been observed in high temperature copper oxide superconductors, iridates, copper oxides spin ladders and recently kagome vanadate superconductors. Such currents induce orbital magnetic moments within the unit cell of these quantum materials that can be detected through their interaction with the neutron spin. In addition to the usual description of orbital moments using point-like local magnetic moments, we here show an alternative description of the neutron magnetic cross-section involving the microscopic currents running between different atomic orbitals. We discuss the corresponding magnetic structure factors and the resulting quantitative differences between both approaches.