Radiofrequency spectroscopy of trapped Bose polarons: crossover from the adiabatic to the diabatic regime

The crossover of the impurity-induced spin dynamics, in trapped Bose polarons subject to radio frequency (rf) pulses of varying intensity, covering the crossover from the adiabatic to the diabatic regime is unraveled. For adiabatic pulses various polaronic excitations and mode-couplings are spectrally resolved. A temporal orthogonality catastrophe manifests in the excitation spectra, for strongly repulsive impurity-bath interactions, associated with a vanishing coherence of the impurity. Interestingly impurity-impurity correlations, for either attractive or strong repulsive couplings, are revealed inducing a spectral shift of the resonances with respect to the single impurity. Considering a heavy impurity, the polaronic peak is accompanied by a series of equidistant side-band resonances, related to interference of the impurity spin dynamics and the sound waves of the bath. By entering the diabatic transfer regime, for an increasing Rabi frequency of the applied rf field, a Lorentzian spectral shape featuring a single polaronic resonance is identified. Our findings on the effects of the external trap, rf pulse and impurity-impurity interactions provide new insights related to contemporary cold-atom experiments.