Dynamical quantum Cherenkov transition of fast impurities in quantum liquids

TL;DR

This paper explores a dynamical quantum Cherenkov transition experienced by a fast impurity in a quantum Bose fluid, revealing a velocity-dependent transition with observable effects in ultracold atom experiments.

Contribution

It uncovers a velocity-induced transition in impurity dynamics, characterized as a dynamical quantum Cherenkov effect, with detailed predictions for experimental detection.

Findings

Identification of a critical velocity for impurity motion transition

Differences in Loschmidt echo and density ripples across regimes

Observable signatures in ultracold atom experiments

Abstract

The challenge of understanding the dynamics of a mobile impurity in an interacting quantum many-body medium comes from the necessity of including entanglement between the impurity and excited states of the environment in a wide range of energy scales. In this paper, we investigate the motion of a finite mass impurity injected into a three-dimensional quantum Bose fluid as it starts shedding Bogoliubov excitations. We uncover a transition in the dynamics as the impurity's velocity crosses a critical value which depends on the strength of the interaction between the impurity and bosons as well as the impurity's recoil energy. We find that in injection experiments, the two regimes differ not only in the character of the impurity velocity abatement, but also exhibit qualitative differences in the Loschmidt echo, density ripples excited in the BEC, and momentum distribution of scattered bosonic particles. The transition is a manifestation of a dynamical quantum Cherenkov effect, and should be experimentally observable with ultracold atoms using Ramsey interferometry, RF spectroscopy, absorption imaging, and time-of-flight imaging.