Physicists detect a hybrid particle held together by uniquely intense 'glue'

MIT physicists have found a hybrid particle in a magnetic material. The particle is made up of two particles. Christine Daniloff is from MIT.

Sometimes two is better than one. Take electron pairs. The material's special superconducting properties are due to the fact that two electrons are bound together. A Cooper pair is a kind of hybrid particle that behaves as one with properties that are greater than the sum of its parts.

MIT physicists have found a hybrid particle in a magnetic material. The hybrid particle is a mix of an electron and a phonon, which is produced from a material's vibrating atoms. The glue was 10 times stronger than any other hybrid known to date.

The particle's exceptional bond suggests that the electron and the phonon could be changed in tandem. The electron could be stimulated and the phonon could be affected by an electronic excitation if it was applied to a hybrid particle. Scientists could use dual control to tune the electrical and magnetism of a material.

The results are relevant because the team identified the hybrid particle in nickel phosphorus trisulfide, a two-dimensional material that has attracted recent interest. Scientists believe the material could one day be used as a new kind of magnetic Semiconductor, which could be made into smaller, faster, and more energy efficient electronics.

Nuh Gedik is a professor of physics at MIT. "Then you could make devices that are different from what they are today."

The results of Gedik's work have been published in the journal Nature Communications. His co-authors include Emre Ergeen, Batyr Ilyas, Dan Mao, Hoi Chun Po, Mehmet Burak Yilmaz, and Senthil Todadri at MIT.

There are sheets of particles.

The field of modern condensed matter physics is focused on the search for interactions at the nanoscale. Superconductivity and other exotic phenomena can be caused by interactions between a material's atoms, electrons, and other particles. Physicists look for the interactions between chemicals and surfaces to make sheets of two-dimensional materials, which could be made as thin as one atomic layer.

A research group in Korea discovered some unexpected interactions in sheets of NiPS3 that became antiferromagnets at very low temperatures. The antiferromagnet's structure resembles a honeycomb lattice of atoms with different spins. A ferromagnetic material is made up of atoms with spins aligned in the same direction.

The group discovered that an exotic excitation became visible when the material was cooled below its antiferromagnetic transition, though the exact nature of the interactions responsible for this was unclear. A group found signs of a hybrid particle, but its exact constituents and relationship with this exotic excitation were not clear.

Gedik and his colleagues wondered if they could detect the hybrid particle by using a super-fast laser to catch their signature motions.

An artist's impression of electrons in the d-orbitals interacting with lattice waves. The electronic cloud of nickel ion is depicted in the structure. The waves come from the structure. The red glowing stripes show the formation of a bound state. Credit: Emre Ergecen.

It is visible magnetically.

Even with the world's fastest camera, the motion of electrons and other particles is too fast. Gedik says the challenge is similar to taking a photo of a person running. The person is still running in the frame and the camera's shutter is not fast enough to take a clear picture.

The team used an ultrafast laser that only lasted 25 femtoseconds, which is 1 millionth of a second. They aimed the laser at the sample of NiPS3. The first pulse was set with a slight delay so that it stimulated the sample, while the second pulse captured the sample's response with a time resolution of 25 femtoseconds. They were able to create ultrafast "movies" from which the interactions of different particles within the material could be deduced.

The amount of light reflected from the sample was measured as a function of time. If hybrid particles are present, this reflection should change. When the sample was cooled below 150 kelvins, it became antiferromagnetic.

When magnetism is turned on, the particle is only visible below a certain temperature.

The team varied the color of the first laser and found that the hybrid particle was visible when the light reflected from the electron moved between two d-orbitals. They looked at the spacing of the periodic pattern visible in the reflected light spectrum and found it matched the energy of a specific type of phonon. The hybrid particle consists of d-orbital electrons and a specific phonon.

The force binding the electron with the phonon is 10 times stronger than what has been estimated for other known electron-phonon hybrid.

One potential way of exploiting this hybrid particle is to allow you to couple to one of the components and indirectly tune the other. You could change the properties of a material by doing that.

Emre Ergeen et al, Magnetically brightened dark electron-phonon bound states in a van der Waals antiferromagnet, Nature Communications, is more information. There is a DOI of 10.1038/s41467-021-27741-3.

Nature Communications is a journal.

Physicists detect a hybrid particle held together by uniquely intense 'glue'.

The document is copyrighted. Any fair dealing for the purpose of private study or research cannot be reproduced without written permission. The content is not intended to be used for anything other than information purposes.