# Observation of coherent multiorbital polarons in a two-dimensional Fermi gas

## TL;DR

This paper reports the first experimental observation of multiorbital polarons in a two-dimensional Fermi gas of ytterbium atoms, revealing their energies, coherence, and long-lived nature, supported by a comprehensive many-body theory.

## Contribution

It provides the first experimental evidence of multiorbital polarons in 2D Fermi gases and develops a theoretical model that matches the observations.

## Key findings

- Long-lived repulsive polarons with decay rates much lower than their energies
- Spectroscopic measurement of attractive and repulsive polaron energies
- Theoretical model accurately describing interorbital interactions in 2D

## Abstract

We report on the experimental observation of multiorbital polarons in a two-dimensional Fermi gas of $^{173}\mathrm{Yb}$ atoms formed by mobile impurities in the metastable $^3\mathrm{P}_0$ orbital and a Fermi sea in the ground-state $^1\mathrm{S}_0$ orbital. We spectroscopically probe the energies of attractive and repulsive polarons close to an orbital Feshbach resonance and characterize their coherence by measuring the quasiparticle residue. For all probed interaction parameters, the repulsive polaron is a long-lived quasiparticle with a decay rate more than 2 orders of magnitude below its energy. We formulate a many-body theory, which accurately treats the interorbital interactions in two dimensions and agrees well with the experimental results. Our work paves the way for the investigation of many-body physics in multiorbital ultracold Fermi gases.