Fermi Polarons as Spectroscopic Probes: From Static to Mobile Impurities

Talk

Impurities immersed in a quantum many-body environment provide a powerful and versatile route to probe its properties. In this talk, I will present a unifying perspective in which Fermi polarons act as spectroscopic sensors across a wide range of physical platforms, from ultracold atoms in optical lattices to dipolar systems and solid-state realizations.

Focusing on radio-frequency spectroscopy as a direct experimental probe, I will discuss how the impurity response encodes key properties of the surrounding medium. A central theme will be the role of impurity mass: starting from the static limit, I will show how finite-mass effects qualitatively modify the spectral response and give rise to new physical regimes. To describe this crossover, we develop a theoretical framework capturing finite-mass corrections and introduce a mass-gap picture that naturally connects heavy and mobile impurity limits.

These ideas are directly relevant for ongoing experiments. I will outline experimental realizations in various systems, and discuss recent progress toward realizing heavy Fermi polarons with ultracold LiCs mixtures in Heidelberg.

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