Impurity-Induced Multibody Resonances in a Bose Gas

Area of Science:

• Atomic, Molecular, and Optical Physics
• Quantum Many-Body Systems

Background:

• Investigating the behavior of identical bosons interacting with a massive impurity is crucial for understanding quantum systems.
• The concept of Bose polarons in cold-atom experiments highlights the need to study impurity-boson interactions.

Purpose of the Study:

• To analyze the impact of impurity-boson interactions on N identical bosons.
• To explore the emergence of effective boson-boson repulsion and its effect on bound states.
• To identify universal features and limitations of multibody bound states involving an impurity.

Main Methods:

• Theoretical investigation of N identical bosons coupled to an infinitely massive impurity.
• Analysis of impurity-boson interactions mediated by a closed-channel dimer.
• Identification of multibody resonances and critical scattering lengths.

Main Results:

• A dynamical impurity-boson interaction induces effective boson-boson repulsion.
• Two universal multibody resonances are demonstrated, marking the appearance and disappearance of bound states for any N.
• A critical scattering length a* is identified, beyond which the trimer bound state vanishes.
• The ground-state energy in the multibody bound-state region is found to be bounded from below, independent of N.

Conclusions:

• Impurity-boson interactions can lead to complex many-body phenomena, including effective repulsion and universal resonances.
• Multibody bound states become increasingly fragile as N increases beyond the dimer state.
• The findings have direct implications for the experimental study of Bose polarons in cold-atom systems.