Global first: Scientists confirm the existence of quantum tornadoes

Physicists have uncovered a new quantum phenomenon, proving for the first time that electrons can form vortex-like structures in momentum space.

This breakthrough, led by researchers at the Universities of Würzburg and Dresden, sheds light on how electrons behave in topological semimetals and may pave the way for energy-efficient quantum technologies.

Understanding how electrons move in materials is central to modern physics. Traditional research focuses on position space, where familiar vortex structures appear in fluids, superfluids, and superconductors.

However, momentum space—which describes electron behavior in terms of energy and movement direction—has remained largely unexplored for such phenomena. Scientists have long theorized that electrons could form vortex-like patterns in momentum space, but until now, experimental confirmation was missing.

Using soft x-ray angle-resolved photoelectron spectroscopy (SX-ARPES), researchers mapped the three-dimensional momentum space of tantalum arsenide (TaAs), a quantum semimetal known for hosting exotic electronic states.

Their findings, published in the journal Physical Review X, revealed the existence of quantum tornadoes—topological vortex lines of orbital angular momentum. Unlike previously studied Weyl points in TaAs, these newly discovered structures form a distinct class of nodal lines pinned to vortex cores.

"When we first saw signs that the predicted quantum vortices actually existed and could be measured, we immediately reached out to our Dresden colleague and launched a joint project," said Dr. Maximilian Ünzelmann, the study’s lead researcher.

The idea that quantum tornadoes could form in momentum space was first proposed by physicist Roderich Moessner nearly a decade ago. He described them as resembling smoke rings, composed of intertwined electron vortices. However, detecting these structures required an innovative approach.

The Würzburg research team enhanced a widely used method called angle-resolved photoemission spectroscopy (ARPES). This technique, rooted in Albert Einstein’s photoelectric effect, involves shining light on a material, extracting electrons, and analyzing their energy and motion. By refining ARPES with quantum tomography, the team reconstructed a detailed 3D image of electron motion in momentum space.

"We analyzed the sample layer by layer, similar to how medical tomography works," said Ünzelmann. "By stitching together individual images, we could confirm that electrons form vortices in momentum space."

This discovery marks a major step in condensed matter physics, proving that quantum materials can support vortex structures beyond position space.

Beyond fundamental physics, these quantum tornadoes could have significant technological implications. The study of orbital angular momentum has gained traction in recent years due to its potential applications in orbitronics—a field that seeks to harness electrons' orbital motion for information processing. Unlike traditional electronics, which rely on electrical charge, orbitronics could transmit data with minimal energy loss.

"This discovery may put topological nodal line semimetals in the spotlight of orbitronics," the researchers noted. If harnessed effectively, the quantum tornado effect could lead to more efficient data transmission in next-generation electronic devices.

The Würzburg-Dresden research network has been instrumental in achieving this milestone. "The experimental detection of the quantum tornado is a testament to ct.qmat’s team spirit," said Professor Matthias Vojta, a theoretical physicist at TU Dresden. "With strong physics hubs in Würzburg and Dresden, we seamlessly integrate theory and experiment. And, of course, almost every physics project today is a global effort—this one included."

The success of this experiment relied on contributions from scientists around the world. The tantalum arsenide sample was grown in the United States and analyzed at PETRA III, a leading research facility at the German Electron Synchrotron (DESY) in Hamburg. A Chinese researcher developed the theoretical framework, while a Norwegian scientist played a key role in the experimental process.

Looking ahead, the research team plans to explore whether TaAs or similar materials can be used to develop functional orbital quantum components. The discovery of quantum tornadoes represents a significant step toward understanding momentum-space physics and its potential applications in future quantum technologies.

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