New optical method for verifying topological phases in magnetic materials

New optical method for verifying topological phases in magnetic materials

A magnetic material is exposed to two laser beams whose electric fields rotate in opposite directions. The material scatters the light back. If there is a difference between the intensity of the scattered light from the two beams, the material is in a topological phase. Credit: Jörg Harms, MPSD

Topological phases are not limited to electronic systems. They can also appear in magnetic materials whose properties are described in terms of magnetic waves – or so-called magnons. However, even though scientists have established techniques for generating and reading magnon currents, they have so far been unable to directly establish a topological magnon phase.

Just as a sound wave travels through air, a magnon can travel through a magnetic material creating a disturbance in its magnetic order. This order can be imagined as a collection of tops that share a particular axis of rotation. The effect of the wave is to slightly tilt the axes around which the peaks spin.

A topological magnon phase is associated with channels that can transport a current of magnons along the edges of the sample. The researchers hope that such edge channels can be used to carry information in future spintronic devices, analogous to how electric currents are used to transmit signals in electronic devices. However, before such technologies can be realized, scientists must find a way to validate whether a magnetic phase is topological or not.

The transatlantic research team studied a class of magnetic materials structurally similar to graphene and exposed them to laser light with either a right- or left-handed polarization, where the laser’s electric field rotates either clockwise or counterclockwise. clockwise or counterclockwise around the laser beam axis.

The researchers analyzed the scattered light from the material and showed that if the scattered intensity is different for the two polarizations, the material is in a topological phase. Conversely, if there is no difference in the intensity of the scattered light, then the material is not in a topological phase. The properties of the scattered light thus act as clear indicators of the topological phases in these magnetic materials.

The technique is easy to implement and can be extended to other quasiparticles, says lead author Emil Viñas Boström: “Raman scattering is a standard experimental technique available in many laboratories, which is one of the strengths of this proposal. the results are quite general and apply equally well to other types of systems consisting of phonons, excitons or photons.”

In the long term, it is hoped that magnons can be used to build more durable technological devices with much lower power consumption: “Using topological magnon currents could reduce the power consumption of future devices by a factor of about 1,000 compared with electronic ones. devices – although there are a lot of issues to be solved before we get to that point,” says Viñas Boström.

The study is published in the journal Physical Review Letters.

More information:
Emil Viñas Boström et al., Direct Optical Probe of Magnon Topology in Two-Dimensional Quantum Magnets, Physical Review Letters (2023). DOI: 10.1103/PhysRevLett.130.026701

Provided by the Max Planck Institute for the Structure and Dynamics of Matter

Citation: New Optical Method for Probing Topological Phases in Magnetic Materials (2023, January 17) Retrieved January 18, 2023 from

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