Environment-limited transfer of angular momentum in Bose liquids

TL;DR

This paper investigates how angular momentum is transferred between a rotating impurity and a bosonic quantum fluid, revealing a critical initial angular momentum beyond which transfer channels become inactive.

Contribution

It introduces a quasiparticle approach based on angulon theory to analyze angular momentum exchange in Bose liquids, highlighting a critical initial angular momentum effect.

Findings

Angular momentum exchange depends on the impurity's initial state.

A critical initial angular momentum threshold exists, halting transfer.

Impurity dressing by environmental excitations enables exchange channels.

Abstract

Impurity motion in a many-body environment has been a central issue in the field of low-temperature physics for decades. In bosonic quantum fluids, the onset of a drag force experienced by point-like objects is due to collective environment excitations, driven by the exchange of linear momentum between the impurity and the many-body bath. In this work we consider a rotating impurity, with the aim of exploring how angular momentum is exchanged with the surrounding bosonic environment. In order to elucidate this issues, we employ a quasiparticle approach based on the angulon theory, which allows us to effectively deal with the non-trivial algebra of quantized angular momentum in presence of a many-body environment. We uncover how impurity dressing by environmental excitations can establish an exchange channel, whose effectiveness crucially depends on the initial state of the impurity. Remarkably, we find that there is a critical value of initial angular momentum, above which this channel effectively freezes.