38 research outputs found
Quench Dynamics and Orthogonality Catastrophe of Bose Polarons
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.Comment: 14 pages, 7 figure
Pump Probe Spectroscopy of Bose Polarons: Dynamical Formation and Coherence
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 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.Comment: 17 pages, 8 figure
Many-Body Dissipative Flow of a Confined Scalar Bose-Einstein Condensate Driven by a Gaussian Impurity
The many-body dissipative flow induced by a mobile aussian impurity
harmonically oscillating within a cigar-shaped Bose-Einstein condensate is
investigated. For very {small and large driving frequencies} the superfluid
phase is preserved. Dissipation is identified, for intermediate driving
frequencies, by the non-zero value of the drag force whose abrupt increase
{signals the spontaneous downstream emission of an array of gray solitons.
After each emission event, typically each of the solitary waves formed decays
and splits into two daughter gray solitary waves that are found to be robust
propagating in the bosonic background for large evolution times.} In
particular, a smooth transition towards dissipation is observed, with the {\it
critical} velocity for solitary wave formation depending on both the
characteristics of the obstacle, namely its driving frequency and width as well
as on the interaction strength. The variance of a sample of single-shot
simulations indicates the fragmented nature of the system; here it is found to
increase during evolution for driving frequencies where the coherent structure
formation becomes significant. Finally, we demonstrate that for fairly large
particle numbers in-situ single-shot images directly capture the gray soliton's
decay and splitting.Comment: 14 pages, 7 figure
Many-body quantum dynamics and induced correlations of Bose polarons
We study the ground state properties and non-equilibrium dynamics of two spinor bosonic impurities immersed in a one-dimensional bosonic gas upon applying an interspecies interaction quench. For the ground state of two non-interacting impurities we reveal signatures of attractive induced interactions in both cases of attractive or repulsive interspecies interactions, while a weak impurity-impurity repulsion forces the impurities to stay apart. Turning to the quench dynamics we inspect the time-evolution of the contrast unveiling the existence, dynamical deformation and the orthogonality catastrophe of Bose polarons. We find that for an increasing postquench repulsion the impurities reside in a superposition of two distinct two-body configurations while at strong repulsions their corresponding two-body correlation patterns show a spatially delocalized behavior evincing the involvement of higher excited states. For attractive interspecies couplings, the impurities exhibit a tendency to localize at the origin and remarkably for strong attractions they experience a mutual attraction on the two-body level that is imprinted as a density hump on the bosonic bath