Emergence of a sharp quantum collective mode in a one-dimensional Fermi polaron

TL;DR

This paper reports the discovery of a long-lived collective mode in a one-dimensional Fermi polaron system, revealing non-dissipative dynamics at specific momentum conditions, observable via ultracold atom experiments.

Contribution

It uncovers a novel sharp collective mode in 1D Fermi polarons at Fermi momentum, challenging the conventional dissipative picture of polaron dynamics.

Findings

Identification of a long-lived collective mode at Fermi momentum

Observation of oscillatory polaronic cloud dynamics

Potential experimental detection via Ramsey interferometry

Abstract

The Fermi-polaron problem of a mobile impurity interacting with fermionic medium emerges in various contexts, ranging from the foundations of Landau's Fermi-liquid theory to electron-exciton interaction in semiconductors, to unusual properties of high-temperature superconductors. While classically the medium provides only a dissipative environment to the impurity, quantum picture of polaronic dressing is more intricate and arises from the interplay of few- and many-body aspects of the problem. The conventional expectation for the dynamics of Fermi polarons is that it is dissipative in character, and any excess energy is rapidly emitted away from the impurity as particle-hole excitations. Here we report a strikingly different type of polaron dynamics in a one-dimensional system of the impurity interacting repulsively with the fermions. When the total momentum of the system equals the Fermi momentum, there emerges a sharp collective mode corresponding to long-lived oscillations of the polaronic cloud surrounding the impurity. This mode can be observed experimentally with ultracold atoms using Ramsey interferometry and radio-frequency spectroscopy.