Switchable X-ray Orbital Angular Momentum from an Artificial Spin Ice

TL;DR

This paper demonstrates that artificial spin ices with specific topological defects can generate switchable orbital angular momentum in X-ray beams, enabling reconfigurable X-ray optical devices for probing magnetic and electronic properties.

Contribution

It introduces a method to produce and control X-ray orbital angular momentum using artificial spin ices with engineered topological defects, a novel approach in X-ray optics.

Findings

Double dislocations in ASI produce even and odd OAM quantum numbers.

Magnetic transitions enable switching of OAM beams with temperature and magnetic field.

ASI-based metasurfaces can be reconfigured for advanced X-ray applications.

Abstract

Artificial spin ices (ASI) have been widely investigated as magnetic metamaterials with exotic properties governed by their geometries. In parallel, interest in X-ray photon orbital angular momentum (OAM) has been rapidly growing. Here we show that a square ASI with a programmed topological defect, a double edge dislocation, imparts OAM to scattered X-rays. Unlike single dislocations, a double dislocation does not introduce magnetic frustration, and the ASI equilibrates to its antiferromagnetic (AF) ground state. The topological charge of the defect differs with respect to the structural and magnetic order; thus, X-ray diffraction from the ASI produces photons with even and odd OAM quantum numbers at the structural and AF Bragg conditions, respectively. The magnetic transitions of the ASI allow the AF OAM beams to be switched on and off by modest variations of temperature and applied magnetic field. These results demonstrate ASIs can serve as metasurfaces for reconfigurable X-ray optics that could enable selective probes of electronic and magnetic properties.