Dresden 2017 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 24: Low-Dimensional Systems: 1D - Theory

TT 24.4: Vortrag

Dienstag, 21. März 2017, 10:15–10:30, HSZ 204

Filling-dependent doublon dynamics in the one-dimensional Hubbard model — •Roman Rausch and Michael Potthoff — I. Institute for Theoretical Physics, University of Hamburg

The fate of a local two-hole doublon excitation in the one-dimensional Fermi-Hubbard model is systematically studied in the entire filling range using the density-matrix renormalization group (DMRG) and the Bethe ansatz. For strong Hubbard interaction U, two holes at the same site form a compound object whose decay is impeded by the lack of phase space. Still, a partial decay is possible on an extremely short time scale where phase-space arguments do not yet apply. We argue that the initial decay and the resulting intermediate state are relevant for experiments performed with ultracold atoms loaded into an optical lattice as well as for CVV Auger-electron spectroscopy. The discussion comprises the mixed ballistic-diffusive real-time propagation of the doublon through the lattice, its partial decay on the short time scale as a function of filling and interaction strength, as well as the analysis of the decay products, which are metastable on the intermediate time scale. The ambivalent role of singly occupied sites is key to understanding the doublon physics: For high fillings, ground-state configurations with single occupancies are recognized to strongly relax the kinematic constraints and to open up decay channels. For fillings close to half filling, however, their presence actually blocks the doublon decay. Finally, we demonstrate that the decay products as well as the doublon propagation should rather be understood in terms of Bethe ansatz eigenstates (spinons and holons).