Pump-probe spectroscopy of Bose polarons: Dynamical formation and coherence

Abstract

We propose and investigate a pump-probe spectroscopy scheme to unveil the time-resolved dynamics of fermionic or bosonic impurities immersed in a harmonically trapped Bose-Einstein condensate. In this scheme a pump pulse initially transfers the impurities from a noninteracting to a resonantly interacting spin state and, after a finite time in which the system evolves freely, the probe pulse reverses this transition. This directly allows us to monitor the nonequilibrium dynamics of the impurities as the dynamical formation of coherent attractive or repulsive Bose polarons and signatures of their induced interactions are imprinted in the probe spectra. We show that for interspecies repulsions exceeding the intraspecies ones a temporal orthogonality catastrophe occurs, followed by enhanced energy redistribution processes, independently of the impurity's flavor. This phenomenon takes place over the characteristic trap timescales. For much longer timescales a steady state is reached characterized by substantial losses of coherence of the impurities. This steady state is related to eigenstate thermalization and it is demonstrated to be independent of the system's characteristics.

Entangling Lattice-Trapped Bosons with a Free Impurity: Impact on Stationary and Dynamical Properties

“…Furthermore, it would be intriguing to study the persistence and possible alterations of the identified spatial configurations in the presence of finite temperature which will impact the coherence of the lattice bosons [88][89][90]. Another perspective is to investigate the relevant radiofrequency spectrum [31,43] in order to capture the emergent polaron properties including their lifetime, residue and effective mass especially in the attractive interaction regimes of bound state formation.…”

“…Another relevant ingredient is the external trapping geometry that the two components experience. Indeed, for harmonically trapped and homogeneous systems remarkable dynamical features of impurity physics include the spontaneous generation of localized patterns [17,[37][38][39], inelastic collisional aspects of driven impurities [40][41][42] with the surrounding and their relaxation at long timescales [43][44][45]. On the other hand, when a lattice potential is introduced the situation becomes more complicated giving rise, among others, to doped insulator physics [46,47] and impurity transport [48][49][50].…”

Artificial atoms from cold bosons in one dimension

“…The second method is called the multi-layer multi-configuration time-dependent Hartree method for atomic mixtures (ML-MCTDHX) [16] (see also a relevant review on the topic [52]). It is a variational approach that has been extensively used, among others, for studying systems with impurities [41,42,[53][54][55][56].…”

Intra- and interband excitations induced residue decay of the Bose polaron in a one-dimensional double-well

“…These systems are inherently related to the so-called polaron concept [40,41], which is originally introduced in the context of a mobile impurity immersed in a quantum many-body environment with the former becoming dressed by the excitations of the bath [42][43][44][45]. So far, notable investigations of the emergent polaron properties in the ultracold atomic realm unveil, for example, their effective mass [35,[46][47][48][49], the underlying excitation spectra [50][51][52][53][54], the existence of bath mediated induced-interactions [55][56][57][58][59][60], as well as the orthogonality catastrophe (OC) mechanism [61][62][63][64][65].…”