Transient dynamics of a one‐dimensional Holstein polaron under the influence of an external electric field

Abstract

Following the Dirac-Frenkel time-dependent variational principle, transient dynamics of a one-dimensional Holstein polaron with diagonal and off-diagonal exciton-phonon coupling in an external electric field is studied by employing the multi-D 2 Ansatz, also known as a superposition of the usual Davydov D 2 trial states. Resultant polaron dynamics has significantly enhanced accuracy, and is in perfect agreement with that derived from the hierarchy equations of motion method. Starting from an initial broad wave packet, the exciton undergoes typical Bloch oscillations. Adding weak exciton-phonon coupling leads to a broadened exciton wave packet and a reduced current amplitude. Using a narrow wave packet as the initial state, the bare exciton oscillates in a symmetric breathing mode, but the symmetry is easily broken by weak coupling to phonons, resulting in a non-zero exciton current. For both scenarios, temporal periodicity is unchanged by exciton-phonon coupling. In particular, at variance with the case of an infinite linear chain, no steady state is found in a finite-sized ring within the antiadiabatic regime. For strong diagonal coupling, the multi-D 2 Anstaz is found to be highly accurate, and the phonon confinement gives rise to exciton localization and decay of the Bloch oscillations.

Eigenstate thermalization and quantum chaos in the Holstein polaron model

“…A second timely motivation to study nonequilibrium problems in electron-phonon coupled systems stems from the experimental advances with time-resolved spectroscopy [47]. Such experiments have stimulated an increased interest in exploring nonequilibrium dynamics of isolated electron-phonon coupled systems theoretically [48][49][50][51][52][53][54][55][56][57][58][59][60][61][62][63][64][65][66]. Among them, systems with a single excited electron coupled to phonons (the so-called polaron case) provide a platform for accurate numerical simulations [49,58,60,67,68], allowing us to demonstrate, for certain nonequilibrium protocols, equilibration [52,58] and indications for thermalization [61].…”

Effect of Off-Diagonal Exciton–Phonon Coupling on Intramolecular Singlet Fission

“…The multiple Davydov trial states with multiplicity M , which are essentially M copies of the corresponding single Davydov Ansatz, [58][59][60][61][62] have been developed for the Holstein model and the spin-boson model. In the two level system description of the iSF process, one of the multiple Davydov trial states, the multi-D 2 Ansatz with multiplicity M , can be constructed as [58,59,63,64]…”

Transient Dynamics of Super Bloch Oscillations of a 1D Holstein Polaron under the Influence of an External AC Electric Field

“…Being strongly dependent on the initial conditions, the motion of the carrier wave packet subject to the DC and AC electric field has been found to exhibit a breathing mode or the typical BOs/SBOs, thus here we discuss the initial conditions before moving on to specific calculations. Effects of initial Gaussian wave packets have been investigated by Caetano et al.…”

“…More recently, cold atoms and Bose–Einstein condensates (BECs) in optical lattices have been revealed as a very convenient quasiparticles to undergo the BOs since the scattering processes can be significantly reduced . To probe the mechanism by which the BOs take place, the dynamics of the carrier wave packet has been extensively studied in various physical systems, including a semiconductor waveguide and a thermo‐optic polymer array subjected to a temperature gradient …”

“…Their work retained full quantum coherence in the description of nonequilibrium dynamics of a polaron . Recently, the crux of transient dynamics of the BOs was laid out in our previous study by employing the multiple Davydov trial states . Since the dynamical control of the SBOs can be realized in the same experimental setup for the engineering of the BOs, it is necessary to extend the successful method for the dynamics of the BOs to study the influence of carrier–phonon coupling on the SBOs .…”