Quench Dynamics and Orthogonality Catastrophe of Bose Polarons

Abstract

We monitor the correlated quench induced dynamical dressing of a spinor impurity repulsively interacting with a Bose-Einstein condensate. Inspecting the temporal evolution of the structure factor three distinct dynamical regions arise upon increasing the interspecies interaction. These regions are found to be related to the segregated nature of the impurity and to the ohmic character of the bath. It is shown that the impurity dynamics can be described by an effective potential that deforms from a harmonic to a double-well one when crossing the miscibility-immiscibility threshold. In particular, for miscible components the polaron formation is imprinted on the spectral response of the system. We further illustrate that for increasing interaction an orthogonality catastrophe occurs and the polaron picture breaks down. Then a dissipative motion of the impurity takes place leading to a transfer of energy to its environment. This process signals the presence of entanglement in the many-body system.

Many-body quantum dynamics and induced correlations of Bose polarons

“…In view of the results of [35] it is tempting to interpret our above findings in terms of an effective potential, V eff (x; g BI ). A valid candidate for such a potential can be constructed as…”

“…To calculate the stationary properties and to track the MB non-equilibrium quantum dynamics of the multicomponent bosonic system discussed above we employ the ML-MCTDHX method [70][71][72]. This is an ab initio variational method for solving the time-dependent MB Schrödinger equation of atomic mixtures and it is based on the expansion of the total MB wavefunction with respect to a time-dependent and variationally optimized basis tailored to capture both the intra-and the interspecies correlations of a multicomponent system [35,65,81,82].…”

“…depends explicitly on the structure factor S 1 (t) of a single impurity allowing for a direct interpretation of the dynamical dressing of the two impurities with respect to the single impurity case discussed in [35]. In the following, = = º    g g g g II and as a consequence =  g 0, =  g 0 is encountered for g II =0 while the general case of equation (12) applies for the case of g II =0.2 analyzed below.…”

“…Experimentally Bose [20][21][22][23][24] and Fermi [12,13,17] polarons have been observed and these experiments confirmed the importance of higher-order correlations for the description of the polaronic properties. The experiments in turn have spurred additional several theoretical investigations which have aimed at describing different polaronic aspects [25,26] by operating e.g.within the Fröhlich model [27][28][29][30][31], effective Hamiltonian approximations [8,[32][33][34], variational approaches [7,9,22,[35][36][37], renormalization group methods [25,38,39] and the path integral formalism [40,41].…”

“…However, the non-equilibrium dynamics of impurities is far less explored and is expected to be dominated by correlation effects which build up in the course of the evolution [34-36, 39, 42-45]. Existing examples include the observation of self-trapping phenomena [46,47], formation of dark-bright solitons [6,42], impurity transport in optical lattices [48][49][50][51], orthogonality catastrophe events [35,52], injection of a moving impurity into a gas of Tonks-Girardeau bosons [53][54][55][56][57][58][59][60] and the relaxation dynamics of impurities [45,61,62]. Besides these investigations, which have enabled a basic description of the quasiparticle states in different interaction regimes, a number of important questions remain open and a full theoretical understanding of the dynamics specifically of Bose polarons is still far from complete.…”