The Joe Orenstein Group has published their findings on antiferromagnetic spin wavepackets in Nature Physics.
The spin of the electron is Nature’s perfect quantum bit, capable of extending the range of information storage beyond “one” or “zero.” Consequently, exploiting the electron’s spin degree of freedom is one of the central goals of quantum information science. Recent progress has shown the potential of spin wavepackets – collective excitations of electron spin – to transport quantum information over large distances in a class of materials known as antiferromagnets. The work reported by Sun et al. (Nature Physics https://doi.org/10.1038/s41567-024-02387-2) is the first to uncover the mechanism by which antiferromagnetic spin wavepackets propagate.
The antiferromagnetic state is one in which electrons order in an alternating spin up and spin down manner. As each spinning electron is a bar magnet, this arrangement produces no net magnetization. (An antiferromagnet will not stick to your refrigerator door). However, spin wavepackets are a disturbance in the perfect alternating arrangement, and carry with them a magnetic field of their own. Although the magnetism of each packet is weak, the long range nature of magnetic forces allows the local disturbance to propagate over large distances. Using pulses of light, Sun et al. were able to capture time-resolved images that reveal that spin wavepackets spread just as ripples propagate from a pebble dropped into a pond of water (see Figure above). Understanding the mechanism that enables spin propagation leads to design rules for all future applications of antiferromagnets to coherent transport of spin information.
The Orenstein Research Group hikes the Steep Ravine trail near Stinson Beach