DATE2025.07.02 #Press Releases

Strong Magnetic Fields Flip Angular Momentum Dynamics in Magnetovortical Matter

Summary

Study shows orbital angular momentum can outweigh spin in strong magnetic fields, reshaping our view of magnetized quantum systems

Angular momentum is a fundamental quantity in physics that describes the rotational motion of objects. In quantum physics, it encompasses both the intrinsic spin of particles and their orbital motion around a point. These properties are essential for understanding a wide range of systems, from atoms and molecules to complex materials and high-energy particle interactions. 

When a magnetic field is applied to a quantum system, particle spins typically align with or against the field. This well-known effect, known as spin polarization, leads to observable phenomena such as magnetization. Until now, it was widely believed that spin played the dominant role in how particles respond to magnetic fields. However, new research challenges this long-held view.

In this vein, Assistant Professor Kazuya Mameda of Tokyo University of Science, Japan, in collaboration with Professor Kenji Fukushima of School of Science, The University of Tokyo and Dr. Koichi Hattori of Zhejiang University, found that under strong magnetic fields, the orbital motion of magnetovortical matter becomes more significant than spin effects, leading to reversing the overall direction of angular momentum. The study will be published in Physical Review Letters on July 01, 2025.

Image title: Spin versus orbital polarization under an external rotation field with varying magnetic field strength
Image caption: (a) In a weak magnetic field, broad cyclotron orbits suppress the orbital contribution, allowing spin polarization to dominate, (b) In strong magnetic fields, tight cyclotron orbits enhance orbital polarization, which overtakes the spin effect and can reverse the overall direction of the angular momentum.

Related Link

Tokyo University of Science

Journals

Journal name	Physical Review Letters
Title of paper	Preponderant Orbital Polarization in Relativistic Magnetovortical Matter