While the formation of electron vortices within quantum materials has been an established scientific understanding, recent advancements have provided definitive evidence of these subatomic particles generating structures akin to tornadoes within momentum space.
Within a quantum substance identified as tantalum arsenide (TaAs), electrons manifest as vortices in momentum space. Attribution: Think-Design / Jochen Thamm.
Momentum space represents a foundational physics construct, elucidating electron locomotion by characterizing energy and trajectory rather than precise spatial placement.
Its analogue, position space, is the domain where phenomena familiar to us, such as the swirling patterns of water or atmospheric cyclones, manifest.
Up to this juncture, even quantum vortices observed in materials had been confined to observations within position space.
Eight years prior, Dr. Roderich Moessner, affiliated with the Max Planck Institute for the Physics of Complex Systems and the Würzburg-Dresden Cluster of Excellence ct.qmat, postulated the potential for a quantum vortex, analogous to a tornado, to materialize within momentum space.
At that juncture, the phenomenon was likened to a smoke ring, owing to its constituent vortical nature, much like smoke rings themselves.
However, the means to empirically quantify these structures remained elusive until the present study.
To facilitate the detection of this quantum tornado in momentum space, Dr. Moessner and his collaborators refined a well-established methodology known as ARPES (angle-resolved photoemission spectroscopy).
“ARPES stands as a cornerstone instrument in the field of experimental solid-state physics,” elucidated Dr. Maximilian Ünzelmann, a researcher associated with Experimentelle Physik VII and the Würzburg-Dresden Cluster of Excellence ct.qmat at the Universität Würzburg.
“This process entails directing radiation onto a material specimen, subsequently liberating electrons, and then meticulously measuring both their kinetic energy and emission angle.”
“This technique affords us a direct visualization of a material’s electronic configuration within momentum space.”
“Through an ingenious adaptation of this procedure, we achieved the capability to ascertain orbital angular momentum.”
The research conducted by the team is featured in the esteemed publication, Physical Review X.
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T. Figgemeier et al. 2025. Imaging Orbital Vortex Lines in Three-Dimensional Momentum Space. Phys. Rev. X 15, 011032; doi: 10.1103/PhysRevX.15.011032
