Self-propulsion of a polaron with an oscillating coupling to its quantum bath

Abstract

Motivated by the quest for active quantum matter, we investigate the dynamics of an impurity immersed in a quantum gas -- a polaron -- whose coupling to the surrounding medium is periodically modulated in time, alternating in sign. By integrating out the bath degrees of freedom, we derive an effective velocity-dependent drag force acting on the impurity. Above a critical modulation frequency, the corresponding drag coefficient becomes negative at low velocities, signaling the onset of self-propulsion. In the classical limit, we characterize this transition as a function of the modulation frequency and the bath chemical potential. We then compute the leading-order quantum corrections to the impurity dynamics and show that, while the transition remains robust, it can be suppressed by sufficiently precise measurements of the impurity position.