Measure the renormalized Bose polaron mass beyond one dimension

Measure and quantitatively characterize the renormalized effective mass of Bose polarons in dimensions d>1, including three-dimensional ultracold-atom realizations, using controlled experimental protocols (e.g., homogeneous box traps and momentum-resolved spectroscopy or dynamical mass extraction), and provide direct comparisons to theoretical predictions across weak- and strong-coupling regimes.

Background

The review highlights that, despite extensive progress in Bose polaron spectroscopy and theory, direct experimental determinations of the effective mass have so far been confined to quasi-1D systems (e.g., Catani et al.). In homogeneous 3D settings, inhomogeneous broadening and finite lifetime have complicated mass measurements. Establishing the effective mass in d>1 would benchmark theoretical methods (e.g., QMC, FRG, GPE, T-matrix) and clarify strong-coupling dressing effects near Feshbach resonances.

The authors suggest that box traps and improved dynamical protocols could enable precise extraction of mass renormalization (e.g., via dipole oscillations or momentum-dependent spectroscopy), allowing systematic tests of subsonic-to-supersonic transitions and related quasiparticle phenomena.

References

We close this review by providing a discussion of open questions in the field that the authors feel are of particular relevance and should be addressed in future research. For example, no measurements of the renormalized polaron mass exist beyond one-dimensional systems, despite being a hallmark signature of strong polaronic dressing.

— Impurities and polarons in bosonic quantum gases: a review on recent progress (2410.09413 - Grusdt et al., 12 Oct 2024) in Section 7 (Outlook)