# Tuning Dissipation and Excitations in Superfluid Fermi Gases with a Moving Impurity

## TL;DR

This paper presents a method to analyze dissipation caused by a moving impurity in superfluid Fermi gases, revealing how different excitations contribute to drag force and dissipation across the BEC-BCS crossover.

## Contribution

It introduces an analytical approach to extract dissipation and dynamical structure factors, mapping critical velocities and distinguishing effects for magnetic impurities.

## Key findings

- Dissipation involves single-particle and collective excitations.
- Critical velocity for dissipation varies across the BEC-BCS crossover.
- Magnetic impurities are immune to collective excitations.

## Abstract

We develop a method to extract the dissipation for a heavy moving impurity immersed in superfluid Fermi gases. The drag force is derived analytically. As a reward, we are able to extract the dynamical structure factor, from which density excitations of the system is carefully examined. We show that dissipations through drag force is associated with two types of excitations, one being single-particle and the other being collective. We map out the critical velocity for dissipation across the BEC-BCS crossover, consistent with existing experiments. For a magnetic impurity, we show that the dissipation is immune to collective excitations. Our study clearly manifests that dissipation and associated excitations can be controlled by coupling superfluid Fermi gases with a moving impurity, and paves the way for further exploring intriguing realm of nonequilibrium phenomena and dissipation dynamics.