SEMINAR+WEBINAR ANNOUNCEMENT: “Finite-temperature quasiparticle properties of the two-dimensional Bose polaron: a T-matrix approach”

Victor Velasco

International School for Advanced Studies (SISSA), Trieste, Italy

“Finite-temperature quasiparticle properties of the two-dimensional Bose polaron: a T-matrix approach”

Abstract

We investigate the finite-temperature properties of a single impurity immersed in a two-dimensional (2D) Bose gas, using an extended non-self-consistent T-matrix approach. This framework incorporates the interaction between the impurity and thermally excited bosons, accounting for the depletion of the 2D superfluid. To accurately describe the 2D Bose gas at finite temperature, we employ a renormalization group (RG) analysis to determine the superfluid density and the Berezinskii-Kosterlitz-Thouless (BKT) transition temperature, marking the onset of superfluidity. We explore how the polaron's energy, quasiparticle residue, and damping evolve with temperature, identifying a discontinuous change in these properties at the BKT transition. This jump, caused by the superfluid density abrupt vanishing at the superfluid- to normal-state transition, highlights the sensitivity of the Bose polaron to the BKT transition. We suggest that this sensitivity could allow the Bose polaron to serve as an experimental probe for detecting the BKT transition temperature in 2D confined ultracold quantum Bose gases. Finally, we analyze the coherence dynamics of the Bose polaron and highlight the interplay between the exponentially large binding energy inherent of the 2D two-body problem, and thermal decoherence, which plays a substantial role in determining the lifetime of the quasiparticle.