Finite-temperature behavior of the Bose polaron

TL;DR

This paper analyzes how the energy and damping of a Bose polaron change with temperature, especially near the Bose-Einstein condensation transition, revealing non-monotonic behavior and sharp damping increases.

Contribution

It provides analytical results for the finite-temperature behavior of the Bose polaron using perturbation theory, highlighting temperature-dependent effects near phase transition.

Findings

Energy exhibits non-monotonic behavior near $T_c$

Damping increases sharply close to $T_c$

Properties strongly depend on temperature near phase transition

Abstract

We consider a mobile impurity immersed in a Bose gas at finite temperature. Using perturbation theory valid for weak coupling between the impurity and the bosons, we derive analytical results for the energy and damping of the impurity for low and high temperatures, as well as for temperatures close to the critical temperature $T_c$ for Bose-Einstein condensation. These results show that the properties of the impurity vary strongly with temperature. In particular, the energy exhibits a non-monotonic behavior close to $T_c$, and the damping rises sharply close to $T_c$. We argue that this behaviour is generic for impurities immersed in an environment undergoing a phase transition that breaks a continuous symmetry. Finally, we discuss how these effects can be detected experimentally.