Fate of an impurity strongly interacting with a thermal Bose gas

Jiří Etrych; Sebastian J. Morris; Simon M. Fischer; Gevorg Martirosyan; Christopher J. Ho; Moritz Drescher; Manfred Salmhofer; Zoran Hadzibabic; Tilman Enss; Christoph Eigen

arXiv · 2508.06493

Fate of an impurity strongly interacting with a thermal Bose gas

Jiří Etrych·Sebastian J. Morris·Simon M. Fischer·Gevorg Martirosyan·Christopher J. Ho·Moritz Drescher·Manfred Salmhofer·Zoran Hadzibabic·Tilman Enss·Christoph Eigen

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Abstract

We spectroscopically study mobile impurities immersed in a homogeneous bosonic bath (a box-trapped Bose gas), varying the bath temperature and the strength of impurity-bath interactions. We compare our results to those for a quasipure Bose-Einstein condensate (BEC), and find that for strong impurity-bath interactions, the spectra narrow with increasing temperature, while the impurity energy shift is suppressed. Near the critical temperature for condensation, many-body effects still play an important role, and only for a nondegenerate bath, the system approaches the classical Boltzmann-gas behavior. The key spectral features are reproduced within the theory of an ideal Bose polaron.

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Jiří Etrych, Sebastian J. Morris, Simon M. Fischer, Gevorg Martirosyan, Christopher J. Ho, Moritz Drescher, Manfred Salmhofer, Zoran Hadzibabic, Tilman Enss, Christoph Eigen. 2025-08-08. Fate of an impurity strongly interacting with a thermal Bose gas. https://arxiv.org/abs/2508.06493

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