August 18, 2022

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Physicists Find “Magnon” Origins in 2D Magnet – Could Prove Useful for Encoding Information

Rice University graduate scholar Lebing Chen used a high-temperature furnace to make chromium triiodide crystals that yielded the 2D supplies for experiments at Oak Ridge National Laboratory’s Spallation Neutron Source. Credit: Jeff Fitlow/Rice University

Topological function might show helpful for encoding data in electron spins.

Rice physicists have confirmed the topological origins of magnons, magnetic options they found three years in the past in a 2D materials that would show helpful for encoding data within the spins of electrons.

The discovery, described in a examine revealed on-line not too long ago within the American Physical Society journal Physical Review X, offers a brand new understanding of topology-driven spin excitations in supplies often called in 2D van der Waals magnets. The supplies are of growing interest for spintronics, a motion within the solid-state electronics neighborhood towards applied sciences that use electron spins to encode data for computation, storage, and communications.

Spin is an intrinsic function of quantum objects and the spins of electrons play a key function in bringing about magnetism.

Rice physicist Pengcheng Dai, co-corresponding writer of the PRX examine, mentioned inelastic neutron-scattering experiments on the 2D materials chromium triiodine confirmed the origin of the topological nature of spin excitations, known as magnons, that his group and others discovered in the material in 2018.

Chromium Triiodide Crystals

Graduate scholar Lebing Chen shows chromium triiodide crystals he made in a Rice University laboratory. Stacked layers of atomically skinny 2D chromium triiodide have uncommon digital and magnetic properties that would show helpful for “spintronic” applied sciences that encode data within the spins of electrons. Credit: Jeff Fitlow/Rice University

The group’s newest experiments at Oak Ridge National Laboratory’s (ORNL) Spallation Neutron Source confirmed “spin-orbit coupling induces asymmetric interactions between spins” of electrons in chromium triiodine, Dai mentioned. “As a result, the electron spins feel the magnetic field of moving nuclei differently, and this affects their topological excitations.”

In van der Waals supplies, atomically skinny 2D layers are stacked like pages in a e-book. The atoms inside layers are tightly bonded, however the bonds between layers are weak. The supplies are helpful for exploring uncommon digital and magnetic behaviors. For instance, a single 2D sheet of chromium triiodine has the identical kind of magnetic order that makes magnetic decals follow a steel fridge. Stacks of three or extra 2D layers even have that magnetic order, which physics name ferromagnetic. But two stacked sheets of chromium triiodine have an reverse order known as antiferromagnetic.

Pengcheng Dai and Lebing Chen

Rice University physicists Pengcheng Dai (left) and Lebing Chen have found that uncommon magnetic options they beforehand observed in 2D chromium triiodide come up from topological options. Credit: Jeff Fitlow/Rice University

That unusual conduct led Dai and colleagues to check the fabric. Rice graduate scholar Lebing Chen, the lead writer of this week’s PRX examine and of the 2018 examine in the identical journal, developed strategies for making and aligning sheets of chromium triiodide for experiments at ORNL. By bombarding these samples with neutrons and measuring the ensuing spin excitations with neutron time-of-flight spectrometry, Chen, Dai and colleagues can discern unknown options and behaviors of the fabric.

In their earlier examine, the researchers confirmed chromium triiodine makes its personal magnetic subject because of magnons that transfer so quick they really feel as if they’re transferring with out resistance. Dai mentioned the newest examine explains why a stack of two 2D layers of chromium triiodide has antiferromagnetic order.

“We found evidence of a stacking-dependent magnetic order in the material,” Dai mentioned. Discovering the origins and key options of the state is essential as a result of it might exist in different 2D van der Waals magnets.

Reference: “Magnetic Field Effect on Topological Spin Excitations in CrI3” by Lebing Chen, Jae-Ho Chung, Matthew B. Stone, Alexander I. Kolesnikov, Barry Winn, V. Ovidiu Garlea, Douglas L. Abernathy, Bin Gao, Mathias Augustin, Elton J. G. Santos, and Pengcheng Dai, 31 August 2021, Physical Review X.
DOI: 10.1103/PhysRevX.11.031047

Additional co-authors embrace Bin Gao of Rice, Jae-Ho Chung of Korea University, Matthew Stone, Alexander Kolesnikov, Barry Winn, Ovidiu Garlea and Douglas Abernathy of ORNL, and Mathias Augustin and Elton Santos of the University of Edinburgh.

The analysis was funded by the National Science Foundation (1700081), the Welch Foundation (C-1839), the National Research Foundation of Korea (2020R1A5A1016518, 2020K1A3A7A09077712), the United Kingdom’s Engineering and Physical Research Council and the University of Edinburgh and made use of amenities offered by the United Kingdom’s ARCHER National Supercomputing Service and the Department of Energy’s Office of Science.

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