Catenaa, Monday, March 09, 2026- Researchers at Heidelberg University have developed a theoretical framework that bridges two previously separate models of quantum impurities in many-body systems.
The work explains how a single particle in a Fermi sea can act as either a mobile quasiparticle or a nearly fixed impurity while still generating order in the surrounding environment.
The team focused on systems where heavy impurities, once considered static, subtly move and induce energy gaps that allow quasiparticles to emerge.
This reconciles the quasiparticle picture, where a particle drags surrounding fermions forming a Fermi polaron, with Anderson’s orthogonality catastrophe, in which immobile impurities distort the system so strongly that quasiparticle formation is blocked.
Using analytical techniques, the researchers showed that even extremely heavy impurities exhibit slight motion, enabling a transition from polaronic to molecular quantum states.
The framework offers a versatile description of impurities across various spatial dimensions and interaction types, making it applicable to ultracold atomic gases, two-dimensional materials, and novel semiconductors.
The findings, published in Physical Review Letters on November 6, 2025, provide a unified perspective on how disorder and motion coexist in quantum systems.
By connecting mobile and static impurity models, the research advances the theoretical understanding of quantum matter and offers guidance for designing future experiments exploring strongly correlated materials.
