Hannover 2016 – wissenschaftliches Programm

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Q: Fachverband Quantenoptik und Photonik

Q 29: Quantum Gases: Bosons III

Q 29.2: Vortrag

Mittwoch, 2. März 2016, 11:30–11:45, e001

Observation of the phononic Lamb shift in the Fröhlich model of a quantum impurity — •Fabián Olivares, Tobias Rentrop, Arno Trautmann, Fred Jendrzejewski, and Markus K. Oberthaler — Kirchhoff-Institut für Physik, Im Neuenheimer Feld 227, 69120 Heidelberg

The interaction of particles with fields can profoundly change their properties. Typical examples are Landau quasiparticles in metals or the QED electron mass renormalisation in vacuum. Ideally these complex phenomena can be studied best when the interaction strengths and particle confinement potentials are freely tuned. We engineer such a system, in which fermionic and bosonic impurities are immersed in a Bose-Einstein condensate (BEC). Its phonon field interacts with the impurities thus changing their effective parameters according to the Fröhlich polaron scenario. Using a dedicated spectroscopy method of Ramsey type we measure the energy shifts of confined impurities induced by the phonon-impurity interactions. These shifts cannot be explained by an effective mass concept alone, but only combined with a phonon-induced Lamb shift. The experimental observations are in excellent agreement with the theoretical expectation.