27 October 2020

A Smooth Transition in a Quantum Gas with Impurities

A quantum impurity in a Fermi gas pulls the surrounding fermions toward itself, generating a quasiparticle called a polaron. Increase the interaction strength, and that same impurity binds to just one fermion instead, adopting a stable molecular state. For a single impurity, theory predicts that this change occurs abruptly, but it was unknown whether the same sudden transition occurs with larger populations of impurities. In collaboration with researchers at the Max Planck Institute of Quantum Optics in Germany, Gal Ness, a graduate student at the Technion – Israel Institute of Technology in Haifa, and colleagues have performed an experiment that shows that the polaron-molecule transition is continuous, with both states coexisting over a range of interaction strengths [1]. Understanding the dynamics of this transition—one of the simplest strongly interacting many-body problems—could shed light on more complex systems.

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Publication
Observation of a Smooth Polaron-Molecule Transition in a Degenerate Fermi Gas
G. Ness, C. Shkedrov, Y. Florshaim, O. K. Diessel, J. von Milczewski, R. Schmidt, and Y. Sagi.
Physics Review X 10, 041019 (2020)
DOI: 10.1103/PhysRevX.10.041019