title: Delocalization and spreading in a nonlinear Stark ladder.
abstract: We study the evolution of a wave packet in a nonlinear Stark ladder. In the absence of nonlinearity all normal modes are spatially localized giving rise to an equidistant eigenvalue spectrum and Bloch oscillations. Nonlinearity induces frequency shifts and mode-mode interactions and destroys localization. For large strength of nonlinearity we observe single-site trapping as a transient, with subsequent explosive spreading, followed by subdiffusion. For moderate nonlinearities an immediate subdiffusion takes place. Finally, for small nonlinearities we find linear Stark localization as a transient, with subsequent subdiffusion. For single-mode excitations and weak nonlinearities, stability intervals are predicted and observed upon variation in the dc bias strength, which affects the short- and the long-time dynamics.
authors.affiliation: Max-Planck Institute for the Physics of Complex Systems, Nöthnitzer Str 38, 01187 Dresden, Germany.
authors.forename: Dmitry O
authors.initials: DO
authors.lastname: Krimer
authors.forename: Ramaz
authors.initials: R
authors.lastname: Khomeriki
authors.forename: Sergej
authors.initials: S
authors.lastname: Flach
mesh_terms: D000465:Algorithms; D003198:Computer Simulation; D008962:Models, Theoretical; D017711:Nonlinear Dynamics; D011789:Quantum Theory