Quantum 2025 – scientific programme

Parts | Days | Selection | Search | Updates | Downloads | Help

TUE: Tuesday Contributed Sessions

TUE 8: Correlated Quantum Matter: Contributed Session to Symposium I

TUE 8.5: Talk

Tuesday, September 9, 2025, 15:15–15:30, ZHG009

Universal theory for heavy impurities in ultracold Fermi gases — •Eugen Dizer, Xin Chen, Emilio Ramos Rodriguez, and Richard Schmidt — Institut für Theoretische Physik, Universität Heidelberg, D-69120 Heidelberg, Germany

Single impurities immersed in a degenerate Fermi gas exhibit fascinating many-body phenomena, such as the polaron-to-molecule transition and Anderson's orthogonality catastrophe (OC). It is known that mobile impurities of finite mass can be described as quasiparticles, so called Fermi polarons. In contrast, Anderson showed in 1967 that the ground state of a static, infinitely heavy impurity in a Fermi sea is orthogonal to the ground state of the system without impurity - a hallmark of the OC and a fundamentally non-perturbative effect. As a result, conventional variational approaches or path integral methods fail to capture this phenomenon accurately. Despite decades of research, a unified approach connecting the quasiparticle description of Fermi polarons with Anderson's OC has remained elusive. In this work, we present a theoretical framework for arbitrary-mass impurities in a Fermi sea that incorporates Anderson's OC, the polaron-to-molecule transition and the quasiparticle picture. Our theory provides new insights into the nature of impurity physics and many-body correlations, describing how quasiparticle behavior and the polaron-to-molecule transition emerge from the OC.

Keywords: Fermi gases; Impurity physics; Fermi polarons; Many-body physics; Orthogonality catastrophe