Breathing dynamics of the Bose polaron in a species-selective harmonic trap

TL;DR

This paper investigates the breathing dynamics of a Bose polaron in a one-dimensional trap, revealing how entanglement and trap asymmetry influence collective excitations and spectrum, with implications for quantum many-body physics.

Contribution

It provides a detailed numerical analysis of the breathing spectrum of a Bose polaron, highlighting the role of entanglement and trap asymmetry in the dynamics, and compares different theoretical approaches.

Findings

Breathing frequency decreases monotonically with coupling strength.

Entanglement is essential for observing certain breathing modes.

Parity symmetry affects the breathing dynamics and spectrum.

Abstract

We perform an extensive numerical study on the breathing dynamics of a few-body Bose polaron setup in a one-dimensional species-selective harmonic trap. The dynamics is triggered by a quench of the impurity trap. The excitation of the background majority atoms is mediated via the majority-impurity interaction. The breathing spectrum is obtained for different numbers of majority particles, several values of the majority-component interaction strengths and trap ratios. It is further compared to the breathing spectrum of a particle-balanced few-body Bose-Bose mixture. In particular, for equal post-quench traps the employed protocol allows to couple states of different center-of-mass parity in contrast to species-symmetric trap quenches. Among the participating eigenstates we identify one having odd center-of-mass parity and even global parity. The breathing frequency induced by this state is a monotonically decreasing function of the coupling parameter. Importantly, in order to be observable it requires the entanglement between the species to be taken into account. We demonstrate this by comparing the numerically exact results obtained by means of the Multi-Layer Multi-Configuration Time-Dependent Hartree Method for Mixtures to the ones of a species mean-field ansatz. The entanglement-sensitive breathing frequency persists also for unequal post-quench traps where the center-of-mass cannot be decoupled. Finally, we analyze the impact of parity symmetry on the breathing dynamics by initializing a state of odd global parity. We evidence a striking resemblance to the ground state breathing dynamics.