Universality of an impurity in a Bose-Einstein condensate

Jonas Rønning, Audun Skaugen, Emilio Hernández-Garcı́a +2 more

Arturo Camacho-Guardian

The propagation of slow light encodes the universal features of a strongly interacting impurity in a Bose-Einstein condensate. The author proposes the use of polariton physics as a nondestructive measurement tool for impurity physics and to investigate polaron physics in the single-impurity limit.

Ranchu Mathew, Eite Tiesinga

Jonas Lampart, Arnaud Triay

We analyze the many-body Hamiltonian describing a mobile impurity immersed in a Bose-Einstein condensate (BEC). Using exact unitary transformations and rigorous error estimates, we show the validity of the Bogoliubov-Fr\"ohlich Hamiltonian for the Bose polaron in the regime of moderately strong, repulsive interactions with a dilute BEC. Moreover, we calculate analytically the universal logarithmic correction to the ground state energy that arises from an impurity mediated phonon-phonon interaction.

Paola Giacconi, Fabio Maltoni B, Roberto Soldati

Arthur Christianen, J. I. Cirac, Richard Schmidt

Similar to an electron in a solid, an impurity in an atomic Bose-Einstein condensate (BEC) is dressed by excitations from the medium, forming a polaron quasiparticle with modified properties. This impurity can also undergo chemical recombination with atoms from the BEC, a process resonantly enhanced when universal three-body Efimov bound states cross the continuum. To study the interplay between these phenomena, we use a Gaussian state variational method able to describe both Efimov physics and arbitrarily many excitations of the BEC. We show that the polaron cloud contributes to bound state formation, leading to a shift of the Efimov resonance to smaller interaction strengths. This shifted scattering resonance marks the onset of a polaronic instability towards the decay into large Efimov clusters and fast recombination, offering a remarkable example of chemistry in a quantum medium.