Finite-range effects in the two-dimensional repulsive Fermi polaron

Abstract

We study the repulsive Fermi polaron in a two-component, two-dimensional system of fermionic atoms inspired by the results of a recent experiment with 173 Yb atoms [N. Darkwah Oppong et al., Phys. Rev. Lett. 122, 193604 (2019)]. We use the diffusion Monte Carlo method to report properties such as the polaron energy and the quasi-particle residue that have been measured in that experiment. To provide insight on the quasi-particle character of the problem, we also report results for the effective mass. We show that the effective range, together with the scattering length, is needed in order to reproduce the experimental results. Using different model potentials for the interaction between the Fermi sea and the impurity, we show that it is possible to establish a regime of universality, in terms of these two parameters, that includes the whole experimental regime. This illustrates the relevance of quantum fluctuations and beyond mean-field effects to correctly describe the Fermi polaron problem.

Polaron in almost ideal molecular Bose-Einstein condensate

“…A somewhat similar trends are visible in the properties of the low-dimensional Fermi polarons [28]. In 2D, particularly, they possess the repulsive branch [29,30], the dressed-molecule state [31,32] when an impurity forms a bound state with a single particle from the Fermi bath. * e-mail: volodyapastukhov@gmail.com…”

Ultra-Dilute Gas of Polarons in a Bose–Einstein Condensate

“…In addition, tunability on the impurity-bath interaction [20,21] allows exploring the strongly interacting regime, inaccessible in the solid-state realm. Theoretically, the problem of a single impurity in a quantum gas have been addressed with several techniques such as mean-field, perturbation theory, renormalization group, modified Gross-Pitaevskii equation, variational ansatzes and field-theory approaches [22][23][24][25][26][27][28][29][30][31][32][33][34][35][36] and numerical approaches such as quantum Monte-Carlo methods [37][38][39][40]. Interestingly, the single-particle polaron problem agrees very well with experiments, where the number of impurities is on the order of five up to ten percent with respect to the total number of atoms of the host gas.…”