Physicists solve a quantum mystery that stumped scientists for decades
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Science News from research organizations Physicists solve a quantum mystery that stumped scientists for decades A long-standing quantum mystery is resolved as physicists reveal how seemingly frozen particles can still spark the emergence of quasiparticles. Date: February 8, 2026 Source: Heidelberg University Summary: Physicists at Heidelberg University have developed a new theory that finally unites two long-standing and seemingly incompatible views of how exotic particles behave inside quantum matter. In some cases, an impurity moves through a sea of particles and forms a quasiparticle known as a Fermi polaron; in others, an extremely heavy impurity freezes in place and disrupts the entire system, destroying quasiparticles altogether. The new framework shows these are not opposing realities after all, revealing how even very heavy particles can make tiny movements that allow quasiparticles to emerge. Share: Facebook Twitter Pinterest LinkedIN Email FULL STORY A new theory from Heidelberg physicists bridges two rival pictures of quantum matter that have puzzled scientists for decades. Credit: AI/ScienceDaily.com Physicists have developed a new theory that brings together two major areas of modern quantum physics. The work explains how a single unusual particle behaves inside a crowded quantum environment known as a many-body system. In this setting, the particle can act either as something that moves freely or as something that remains nearly fixed within a vast collection of fermions, often called a Fermi sea. Researchers at the Institute for Theoretical Physics at Heidelberg University created this framework to explain how quasiparticles form and to link two quantum states that were previously thought to be incompatible. They say the results could strongly influence ongoing experiments in quantum matter. In quantum many-body physics, scientists have long debated how impurities behave when surrounded by large numbers of other particles. These impurities can be unusual electrons or atoms (i.e., exotic electrons or atoms). One widely used explanation is the quasiparticle model. In this picture, a single particle moves through a sea of fermions such as electrons, protons, or neutrons and constantly interacts with those around it. As it travels, it pulls nearby particles along with it, creating a combined entity called a Fermi polaron. Although it behaves like a single particle, this quasiparticle arises from the shared motion of the impurity and its surroundings.
As Eugen Dizer, a doctoral candidate at Heidelberg University, notes, this idea has become central to understanding strongly interacting systems ranging from ultracold gases to solid materials and nuclear matter.
When Heavy Particles Disrupt the System A very different scenario appears in a phenomenon known as Anderson's orthogonality catastrophe. This occurs when an impurity is so heavy that it barely moves at all. Its presence dramatically alters the surrounding system. The wave functions of the fermions change so extensively that they lose their original form, creating a complicated background where coordinated motion breaks down. Under these conditions, quasiparticles cannot form. Until now, physicists have not had a clear theory that links this extreme case with the mobile impurity picture. By applying a range of analytical tools, the Heidelberg team has managed to connect these two descriptions within a single framework.
Small Motions With Big Consequences "The theoretical framework we developed explains how quasiparticles emerge in systems with an extremely heavy impurity, connecting two paradigms that have long been treated separately," explains Eugen Dizer, who works in the Quantum Matter Theory group led by Prof.
Dr Richard Schmidt. A key insight behind the theory is that even very heavy impurities are not perfectly still. As their surroundings adjust, these particles undergo tiny movements. Those slight shifts create an energy gap that makes it possible for quasiparticles to form, even in a strongly correlated environment. The researchers also showed that this process naturally accounts for the transition from polaronic states to molecular quantum states. Implications for Quantum Experiments Prof. Schmidt says the new results offer a flexible way to describe impurities that can be applied across different dimensions and interaction types. "Our research not only advances the theoretical understanding of quantum impurities but is also directly relevant for ongoing experiments with ultracold atomic gases, two-dimensional materials, and novel semiconductors," he adds. The study was conducted as part of Heidelberg University's STRUCTURES Cluster of Excellence and the ISOQUANT Collaborative Research Centre 1225. The findings were published in the journal Physical Review Letters. RELATED TOPICS Matter & Energy Physics Nanotechnology Quantum Physics Weapons Technology Telecommunications Nuclear Energy Graphene Materials Science RELATED TERMS Quantum computer Introduction to quantum mechanics Quantum entanglement Physics Robot Conflict resolution Particle physics Quantum dot Story Source: Materials provided by Heidelberg University. Note: Content may be edited for style and length. Journal Reference: Xin Chen, Eugen Dizer, Emilio Ramos Rodríguez, Richard Schmidt. Mass-Gap Description of Heavy Impurities in Fermi Gases.
Physical Review Letters, 2025; 135 (19) DOI: 10.1103/h2f7-dhjh Cite This Page: MLA APA Chicago Heidelberg University. "Physicists solve a quantum mystery that stumped scientists for decades." ScienceDaily. ScienceDaily, 8 February 2026. . Heidelberg University. (2026, February 8). Physicists solve a quantum mystery that stumped scientists for decades. ScienceDaily. Retrieved February 8, 2026 from www.sciencedaily.com/releases/2026/02/260208011010.htm Heidelberg University. "Physicists solve a quantum mystery that stumped scientists for decades." ScienceDaily. www.sciencedaily.com/releases/2026/02/260208011010.htm (accessed February 8, 2026). Explore More from ScienceDaily RELATED STORIES Scientists May Have Found Dark Matter After 100 Years of Searching Nov. 29, 2025 Nearly a century after astronomers first proposed dark matter to explain the strange motions of galaxies, scientists may finally be catching a glimpse of it. A University of Tokyo researcher ...
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