42 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
Phase Diagram, Stability and Magnetic Properties of Nonlinear Excitations in Spinor Bose–Einstein Condensates
We present the phase diagram, the underlying stability and magnetic properties as well as the dynamics of nonlinear solitary wave excitations arising in the distinct phases of a harmonically confined spinor F = 1 Bose-Einstein condensate. Particularly, it is found that nonlinear excitations in the form of dark-dark-bright solitons exist in the antiferromagnetic and in the easy-axis phase of a spinor gas, being generally unstable in the former while possessing stability intervals in the latter phase. Dark-bright-bright solitons can be realized in the polar and the easy-plane phases as unstable and stable configurations respectively; the latter phase can also feature stable dark-dark-dark solitons. Importantly, the persistence of these types of states upon transitioning, by means of tuning the quadratic Zeeman coefficient from one phase to the other is unravelled. Additionally, the spin-mixing dynamics of stable and unstable matter waves is analyzed, revealing among others the coherent evolution of magnetic dark-bright, nematic dark-bright-bright and dark-dark-dark solitons. Moreover, for the unstable cases unmagnetized or magnetic droplet-like configurations and spin-waves consisting of regular and magnetic solitons are seen to dynamically emerge remaining thereafter robust while propagating for extremely large evolution times. Interestingly, exposing spinorial solitons to finite temperatures, their anti-damping in trap oscillation is showcased. It is found that the latter is suppressed for stronger bright soliton component \u27fillings\u27. Our investigations pave the wave for a systematic production and analysis involving spin transfer processes of such waveforms which have been recently realized in ultracold experiments