12 Jun 2023 Mon 10 am

An impurity in a Bose gas is commonly referred to as Bose polaron. For a dilute Bose gas its properties are expected to be universal, that is dependent only on a few parameters characterizing the boson-impurity interactions. When boson-impurity interactions are weak, it has been known for some time that the properties of the polaron depend only on the scattering length of these interactions. In this talk I will examine stronger boson-impurity interactions, keeping their range finite. Mean field turns out to be a good approximation in this case and the problem can be solved analytically using the Gross-Pitaevskii equation. It will be demonstrated that for attractive interactions between impurity and the bosons up to and including the unitary point of these interactions, all static properties of a Bose polaron in a dilute Bose gas can be calculated in terms of the scattering length and an additional parameter which characterizes the range of the impurity-boson interactions. Using the analytical solution to the Gross-Pitaevskii equation it is possible to produce explicit expressions for the energy and other properties of polaron for the case when the impurity-boson scattering length is tuned to unitarity. Finally, I will discuss our recent results on comparison between the Gross-Pitaevskii equation and the Diffusion Monte Carlo as well as the calculation of the effective mass and the interaction energy between polarons at unitarity.

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