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  • Letter
  • Open Access

Quantum beat spectroscopy of repulsive Bose polarons

A. M. Morgen1, S. S. Balling1, K. Knakkergaard Nielsen2, T. Pohl1,3, G. M. Bruun1, and J. J. Arlt1

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Phys. Rev. Research 7, L022002 – Published 2 April, 2025

DOI: https://doi.org/10.1103/PhysRevResearch.7.L022002

Abstract

The physics of impurities in a bosonic quantum environment is a paradigmatic and challenging many-body problem. Here, this problem is investigated for impurities with strong repulsive interactions based on Ramsey interferometry in a quantum degenerate gas of K39 atoms. We observe revivals in the amplitude of the interferometric signal and identify them as beat signals between two coexisting quasiparticle branches, the attractive and repulsive polarons. The interferometric signal allows for an extraction of their energies for a wide range of interaction strengths, thus resolving outstanding discrepancies in earlier spectroscopic measurements. Furthermore, we identify several dynamical regimes in the formation of the repulsive Bose polaron. Our results improve the understanding of quantum impurities interacting strongly with a bosonic environment and show how short-lived nonequilibrium many-body states can be probed using quantum beat spectroscopy.

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Phys. Rev. Research 7, L022002– Published 2 April, 2025
  • Received 27 October 2023
  • Revised 4 December 2024
  • Accepted 19 March 2025
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Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.

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